CASCADE COMMUNICATIONS CORP
SC 13D, 1997-04-10
COMPUTER COMMUNICATIONS EQUIPMENT
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                                UNITED STATES 
                      SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C. 20549


                                  SCHEDULE 13D

                   UNDER THE SECURITIES EXCHANGE ACT OF 1934

                             (AMENDMENT NO. _____)*


                          ASCEND COMMUNICATIONS, INC.
- -------------------------------------------------------------------------------
                                (Name of Issuer)

                    Common Stock, $.001 Par Value Per Share
- -------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                 043491 10 9
            --------------------------------------------------------
                                (CUSIP Number)

Debra A. Buxbaum, Testa, Hurwitz & Thibeault, LLP, High Street Tower, 125 High
                   Street, Boston, MA 02110  (617) 248-7000
- -------------------------------------------------------------------------------
(Name, Address and Telephone Number of Person Authorized to Receive Notices 
                              and Communications)

                                March 30, 1997
- -------------------------------------------------------------------------------
            (Date of Event which Requires Filing of this Statement)


If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-1(b)(3) or (4), check the following box [_].



NOTE:  Six copies of this statement, including all exhibits, should be filed
with the Commission.  See Rule 13d-1(a) for other parties to whom copies are to
be sent.

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).
<PAGE>
 
- -----------------------                                  ---------------------
  CUSIP NO. 043491 10 9                                     PAGE 2 OF 14 PAGES
- -----------------------                                  ---------------------
 
                                 SCHEDULE 13D

- ------------------------------------------------------------------------------
      NAME OF REPORTING PERSON
 1    

        Cascade Communications Corp.



      S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON  04-3099677
- ------------------------------------------------------------------------------
      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
 2                                                              (a) [_]
                                                                (b) [_]
                                                 
- ------------------------------------------------------------------------------
      SEC USE ONLY
 3
 

- ------------------------------------------------------------------------------
      SOURCE OF FUNDS*
 4    
      WC, BK, OO

- ------------------------------------------------------------------------------

      CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED        [_]
      PURSUANT TO ITEMS 2(d) or 2(e)                                
 5    
      

- ------------------------------------------------------------------------------

      CITIZENSHIP OR PLACE OF ORGANIZATION
 6    
      State of Delaware

- ------------------------------------------------------------------------------
                          SOLE VOTING POWER
                     7   
                          24,025,741 (acquisition of such shares is conditioned
                          upon the occurrence of certain events specified in
                          that certain Ascend Stock Option Agreement dated March
                          30, 1997 filed as Exhibit 2 to this Schedule 13D)

      SHARES       -----------------------------------------------------------
                          SHARED VOTING POWER
   BENEFICIALLY      8
                          6,608,172
     OWNED BY
                   -----------------------------------------------------------
       EACH               SOLE DISPOSITIVE POWER 24,025,741 (acquisition of such
                          shares is conditioned upon the occurrence of certain
    REPORTING             events specified in that certain Ascend Stock Option
                     9    Agreement dated March 30, 1997 filed as Exhibit 2 to
                          this Schedule 13D)
      PERSON                          
                    -----------------------------------------------------------
                          SHARED DISPOSITIVE POWER
       WITH          10
                          -0-
- ------------------------------------------------------------------------------
      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
11  
      30,633,913

- ------------------------------------------------------------------------------
      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
12                  
      [_]
 
- ------------------------------------------------------------------------------
      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
13    
      20.5%

- ------------------------------------------------------------------------------
      TYPE OF REPORTING PERSON*
14
      CO

- ------------------------------------------------------------------------------

                     *SEE INSTRUCTION BEFORE FILLING OUT!
         INCLUDE BOTH SIDES OF THE COVER PAGE, RESPONSES TO ITEMS 1-7
     (INCLUDING EXHIBITS) OF THE SCHEDULE, AND THE SIGNATURE ATTESTATION.
<PAGE>
 
- -----------------------                                  ---------------------
  CUSIP NO. 043491 10 9                                     PAGE 3 OF 14 PAGES
- -----------------------                                  ---------------------
 
        Neither the filing of this statement on Schedule 13D nor any of its
contents shall be deemed to constitute an admission by Cascade Communications
Corp. that it is the beneficial owner of any of the Common Stock referred to
herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as
amended (the "Act"), or for any other purpose, and such beneficial ownership is
expressly disclaimed.

ITEM 1.  SECURITY AND ISSUER

        This statement on Schedule 13D relates to the Common Stock, $.001 par
value per share (the "Common Stock"), of Ascend Communications, Inc., a Delaware
corporation (the "Issuer"). The principal executive offices of the Issuer are
located at One Ascend Plaza, 1701 Harbor Bay Parkway, Alameda, California 94502.

ITEM 2.  IDENTITY AND BACKGROUND

        (a)  The name of the person filing this statement is Cascade
Communications Corp., a Delaware corporation ("Cascade").

        (b)  The address of the principal office and principal business of
Cascade is 5 Carlisle Street, Westford, Massachusetts 01886. Cascade develops,
manufactures, markets and supports a family of high performance, multi-service
wide area network switches that enable public service providers and private
network managers to provide cost-effective, high-speed data, video and voice
communications services to end users.

        (c)  Set forth in Schedule A is an appendix to Item 2 setting forth, to
Cascade's knowledge as of the date hereof, the name and present principal
occupation or employment and the name, principal business address of any
corporation or other organization in which such employment is conducted, of each
of Cascade's directors and executive officers as of the date hereof. The
information contained in Schedule A is incorporated herein by reference.

        (d)  During the past five years, neither Cascade nor, to Cascade's
knowledge, any person named in Schedule A to this Schedule 13D, has been
convicted in a criminal proceeding (excluding traffic violations or similar
misdemeanors).

        (e)  During the past five years, neither Cascade nor, to Cascade's
knowledge, any person named in Schedule A to this Schedule 13D, was a party to a
civil proceeding of a judicial or administrative body of competent jurisdiction
as a result of which such person was or is subject to a judgment, decree or
final order enjoining future violations of, or prohibiting or mandating activity
subject to, federal or state securities laws or finding any violation with
respect to such laws.

        (f)  All of the directors and executive officers of Cascade named in
Schedule A to this Schedule 13D are citizens of the United States.

ITEM 3.  SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION

        This statement on Schedule 13D relates to (i) an option granted to
Cascade by the Issuer to purchase shares of Common Stock from the Issuer as
described in Item 4 below (the "Ascend Stock Option") and (ii) to certain voting
arrangements between Ascend, Cascade and certain stockholders of the Issuer as
described in Item 4 below.
<PAGE>
 
- -----------------------                                  ---------------------
  CUSIP NO. 043491 10 9                                     PAGE 4 OF 14 PAGES
- -----------------------                                  ---------------------


        The Stock Option Agreements. The Ascend Stock Option entitles Cascade
to purchase up to 24,025,741 shares of Issuer Common Stock under the
circumstances specified in the Ascend Stock Option, as described in Item 4, by
exchanging therefor shares of Cascade's Common Stock at the rate of 1.833
shares of Cascade Common Stock for each share of Issuer Common Stock subject
to such option and/or, at Cascade's election, by paying cash of $52.00 per
share. The number of shares of Common Stock subject to the Ascend Stock Option
will be equal to 19.9% of the total outstanding shares of Issuer Common Stock
as of March 30, 1997, subject to adjustment as provided in said Ascend Stock
Option. It is presently anticipated that any purchases of the Issuer's Common
Stock for which Cascade elects to pay cash would be made with funds generated
by a combination of available working capital, bank or other borrowings and/or
the sale, in whole or in part, of shares of Common Stock acquired upon
exercise of the Ascend Stock Option. If Cascade were to elect to pay the
exercise price by delivery of shares of Cascade Common Stock, such shares
would be newly-issued after approval of such issuance by Cascade's board of
directors. The foregoing summary of the Ascend Stock Option is qualified in
its entirety by reference to the copy of the Ascend Stock Option Agreement
included as Exhibit 2 to this Schedule 13D and incorporated herein in 
                             ---------
its entirety by reference. If the Merger is consummated pursuant to the
Agreement and Plan of Reorganization dated as of March 30, 1997, by and among
Issuer, Catskill Merger Corporation and Cascade (the "Merger Agreement"), the
Ascend Stock Option will not be exercised. No monetary consideration was paid
by Cascade to the Issuer for such option.

        As an inducement to the Issuer to enter into the Merger Agreement,
Issuer and Cascade have also entered into a Cascade Stock Option Agreement,
which entitles the Issuer to purchase up to 18,765,939 shares of Cascade Common
Stock under the circumstances specified in the Cascade Stock Option Agreement
between Cascade and the Issuer by exchanging therefor shares of Issuer Common
Stock at the rate of 0.70 of a share of Issuer Common Stock for each share of
Cascade Common Stock subject to such option and/or, at Issuer's election, by
paying cash of $36.40 per share. The foregoing summary of the Cascade Stock
Option Agreement is qualified in its entirety by reference to the copy of the
Cascade Stock Option Agreement included as Exhibit 1 to this Schedule 13D and
                                           ---------
incorporated herein in its entirety by reference. If the Merger is consummated
pursuant to the Merger Agreement, the Cascade Stock Option will not be
exercised. No monetary consideration was paid by the Issuer to Cascade for such
option.

        The Voting Agreements.   Also as an inducement to Cascade to enter into
the Merger Agreement, the all of the directors and executive officers (the
"Voting Agreement Stockholders") of the Issuer have entered into an Ascend
Director and Officer Stock Voting Agreement (collectively the "Ascend Voting
Agreements") with Cascade. Pursuant to each Voting Agreement, the Voting
Agreement Stockholders have agreed to vote the shares of Issuer Common Stock
owned by them (i) in favor of the issuance of the shares of Issuer Common Stock
pursuant to the Merger Agreement and (ii) against approval of any proposal made
in opposition to or competition with consummation of the Merger. The Voting
Agreement Stockholders have also irrevocably appointed Cascade as their lawful
attorney and proxy to vote the shares of Issuer Common Stock owned by the Voting
Agreement Stockholders in the manner described in the previous sentence. The
Voting Agreements each terminates upon the earlier to occur of the Effective
Time or the termination of the Merger Agreement. The name of each Voting
Agreement Stockholder and the number of outstanding shares of Issuer Common
Stock beneficially held by such stockholder as of March 24, 1997 (including an
aggregate of 4,796,700 shares issuable upon exercise of stock options held by
the parties to the Ascend Voting Agreements) is set forth in Schedule B hereto
which is hereby incorporated by this reference. No monetary consideration was
paid by Cascade to the Issuer or to the parties to the Ascend Voting
Agreements for the Ascend Voting Agreements. The
<PAGE>
 
- -----------------------                                  ---------------------
  CUSIP NO. 043491 10 9                                   PAGE 5 OF 14 PAGES
- -----------------------                                  ---------------------

foregoing summary of each of the Ascend Voting Agreements is qualified in its
entirety by reference to the copy of the form of Ascend Voting Agreement
included as Exhibit 4 of this Schedule 13D and incorporated herein in its
            ---------
entirety by reference. Inasmuch as Cascade's voting rights under the Ascend
Voting Agreements are limited solely to certain matters related to the Merger,
and Cascade has no economic interest in or dispositive power over the shares of
the Issuer's Common Stock covered thereby, and such shares may be sold by the
holders thereof, Cascade expressly disclaims beneficial ownership of the shares
of Common Stock of the Issuer covered by the Voting Agreements. As an inducement
to Issuer to enter into the Merger Agreement, all of the directors and executive
officers of Cascade have entered into a Cascade Director and Officer Stock
Voting Agreement dated as of March 30, 1997 with the Issuer, the substance of
which is substantially similar to the substance of the Ascend Voting
Agreements. A copy of the form of Cascade Director and Officer Stock Voting
Agreement is included as Exhibit 3 of this Schedule 13D and incorporated herein
                         ---------
in its entirety by reference.

        Affiliate Agreements.   Also in connection with the Merger Agreement,
the Voting Agreement Stockholders and the directors and executive officers of
Cascade have each entered into a Director, Officer and Stockholder Agreement
with Ascend (collectively, the "Agreements") pursuant to which each person has
agreed not to sell, exchange, transfer, pledge, dispose or otherwise reduce
its risk relative to any shares of Issuer Common Stock or other equity
securities of Issuer (and Cascade Common Stock with respect to its directors
and executive officers) owned by it during the period beginning on the date 30
days prior to the Closing Date (as defined in the Merger Agreement) and ending
on the day after Ascend has published financial results covering at least 30
days of combined operations of Ascend and Cascade in the form of a quarterly
earnings report, an effective registration statement filed with the Securities
and Exchange Commission ("Commission"), a report to the Commission on Form 10-
K, 10-Q or 8-K, or any other public filing or announcement which includes the
combined results of operations. The foregoing summary of the Agreements is
qualified in its entirety by reference to the forms of the Agreements included
as Exhibits 5 and 6 of this Schedule 13D and incorporated herein in its
   ----------------
entirety by reference.

ITEM 4.  PURPOSE OF TRANSACTION

        As stated above, the Stock Options and the Voting Agreements were
entered into, in connection with the execution of the Merger Agreement. Upon
consummation of the Merger pursuant to the Merger Agreement, which is subject to
customary conditions including, without limitation, approval of the
stockholders of Cascade and the Issuer, approvals of regulatory agencies, and
the satisfaction or waiver of various other terms and conditions, Catskill
Merger Corporation, a wholly-owned subsidiary of the Issuer, will be merged
with and into Cascade, which will be the surviving corporation. As a result,
Cascade will become a wholly-owned subsidiary of the Issuer, and each share of
the Cascade's Common Stock then outstanding will be converted into the right
to receive 0.7 (the "Exchange Ratio") share of Issuer Common Stock (and a
proportionate cash payment in lieu of any fractional shares). At the effective
time of the Merger pursuant to the Merger Agreement, any outstanding, but
unexercised options or rights to purchase Common Stock will be assumed by the
Issuer and will become options or rights to acquire shares of Issuer Common
Stock, as adjusted to reflect the Exchange Ratio. The Merger Agreement
provides that the Ascend Board of Directors will elect Messrs. Daniel E.
Smith, Paul J. Ferri and Gururaj Deshpande, each of whom is a current director
of Cascade, to the Issuer's Board of Directors effective upon the consummation
of the Merger. In addition, following the Merger, certain executive officers
of Cascade will become executive officers and key management employees of the
Issuer.

        Subject to certain limitations, the Ascend Stock Option is exercisable,
in whole or in part, at any time or from time to time after the occurrence of an
event (a "Trigger Event") which causes a
<PAGE>
 
- -----------------------                                  ---------------------
  CUSIP NO. 043491 10 9                                   PAGE 6 OF 14 PAGES
- -----------------------                                  ---------------------

Termination Fee or Post-Termination Fee to become payable to Cascade by the
Issuer under the Merger Agreement. A Trigger Event will be deemed to have
occurred and the Ascend Stock Option will become exercisable under the following
circumstances:

        (1)  upon the termination of the Merger Agreement by Cascade if (A)(i)
the Board of Directors of the Issuer shall have withdrawn or modified its
recommendation of the Merger Agreement or the Merger in a manner adverse to
Cascade; (ii) an Alternative Transaction (as defined below) involving the Issuer
shall have taken place or the Board of Directors of the Issuer shall have
recommended such an Alternative Transaction (or a proposal or offer therefor) to
the stockholders of the Issuer or shall have publicly announced its intention to
recommend such an Alternative Transaction (or a proposal or offer therefor) or
to engage in an Alternative Transaction; or (iii) a tender offer or exchange
offer for twenty percent (20%) or more of the outstanding shares of the Common
Stock shall have been commenced or a registration statement with respect thereto
shall have been filed (other than by Cascade or an affiliate thereof) and the
Board of Directors of the Issuer shall have (x) recommended that the
stockholders of the Issuer tender their shares in such tender or exchange offer
or (y) publicly announced its intention to take no position with respect to such
tender offer, and (B) at the time of the event giving rise to the right of
Cascade to terminate, an Alternative Transaction involving the Issuer shall have
been announced or proposed which shall not have been absolutely and
unconditionally withdrawn and abandoned; or

        (2)  upon the termination of the Merger Agreement by Cascade if the
Issuer shall have willfully or intentionally breached any representation,
warranty, covenant or agreement on the part of the Issuer set forth in the
Merger Agreement, which breach, if uncured, would cause any of the conditions to
the closing of the Merger not to be satisfied, and such breach is incapable of
being cured or, if capable of being cured, shall not have been cured within ten
(10) business days following receipt by the Issuer of written notice of such
breach from Cascade, and at the time of the event giving rise to the right of
Cascade to terminate, an Alternative Transaction involving the Issuer shall have
been announced or proposed which shall not have been absolutely and
unconditionally withdrawn and abandoned; or

        (3)  upon the termination of the Merger Agreement by the Issuer as a
result of the failure to receive the requisite vote for the approval of the
issuance of Issuer Common Stock in the Merger by the stockholders of the Issuer,
and at the time of the event giving rise to the right of the Issuer to
terminate, an Alternative Transaction involving the Issuer shall have been
announced or proposed which shall not have been absolutely and unconditionally
withdrawn and abandoned.

        (4)  after termination of the Merger Agreement by Cascade as a result of
the failure to receive the requisite vote for the issuance of shares of Issuer
Common Stock pursuant to the Merger Agreement by the stockholders of the Issuer,
if Cascade delivers written notice of such termination to the Issuer within
twenty (20) days after the applicable meeting of stockholders of the Issuer,
and, at the time of the event giving rise to the right of Cascade to terminate
the Merger Agreement, an Alternative Transaction involving the Issuer shall have
been announced or proposed which shall not have been absolutely and
unconditionally withdrawn and abandoned, and the Issuer within one hundred
eighty (180) days after such termination enters into a definitive written merger
or other business combination agreement with the offeror in such Alternative
Transaction (or any affiliate thereof) or recommends that the stockholders of
the Issuer tender their shares of the Issuer's capital stock in response to a
tender or exchange offer providing for an Alternative Transaction by such
Offeror (or any affiliate thereof) .

        An "Alternative Transaction" involving the Issuer means (i) a
transaction or series of transactions pursuant to which any person or group (as
such term is defined under the Securities Exchange Act of 1934, as amended),
other than Cascade, or any affiliate thereof (a "Third Party"),
<PAGE>
 
- -----------------------                                  ---------------------
  CUSIP NO. 043491 10 9                                   PAGE 7 OF 14 PAGES
- -----------------------                                  ---------------------

acquires (or would acquire upon completion of such transaction or series of
transactions) more than twenty percent (20%) of the equity securities or voting
power of the Issuer or any of its material subsidiaries, pursuant to a tender
offer or exchange offer or otherwise, (ii) a merger, consolidation, share
exchange or other business combination involving the Issuer or any of its
material subsidiaries pursuant to which any Third Party acquires ownership (or
would acquire ownership upon consummation of such merger, consolidation, share
exchange or other business combination) of more than twenty percent (20%) of the
outstanding equity securities or voting power of the Issuer or any of its
material subsidiaries or of the entity surviving such merger or business
combination or resulting from such consolidation, (iii) any other transaction or
series of transactions pursuant to which any Third Party acquires (or would
acquire upon completion of such transaction or series of transactions) control
of assets of the Issuer or any of its material subsidiaries (including, for this
purpose, outstanding equity securities of subsidiaries of such party) having a
fair market value equal to more than twenty percent (20%) of the fair market
value of all the consolidated assets of the Issuer immediately prior to such
transaction or series of transactions, or (iv) any transaction or series of
transactions pursuant to which any Third Party acquires (or would acquire upon
completion of such transaction or series of transactions) control of the Board
of Directors of the Issuer or by which nominees of any Third Party are (or would
be) elected or appointed to a majority of the seats on the Board of Directors of
the Issuer.

        With certain exceptions, the Ascend Stock Option terminates upon the
occurrence of the earlier of the following: (i) the effective time of the
Merger, (ii) the termination of the Merger Agreement under circumstances which
do not constitute a Trigger Event, and (iii) 270 days after the Issuer receives
written notice of the occurrence of a Trigger Event. Notwithstanding the
foregoing, the Ascend Stock Option will remain exercisable for a period of 180
days after the date on which it becomes exercisable after a termination of the
Merger Agreement by Cascade as described in the paragraph (4) of this Item 4. In
addition, the Ascend Stock Option exercise period is automatically extended if
exercise of the Ascend Stock Option is prohibited or restrained for certain
legal reasons. The Ascend Stock Option may not be exercised if Cascade is in
material breach of its material representations, warranties, covenants or
agreements in the Ascend Stock Option Agreement or the Merger Agreement.

        At any time when the Ascend Stock Option is exercisable, Cascade has the
right to "put" the Ascend Stock Option back to the Issuer. Under these "put"
provisions, Cascade has the right to require the Issuer to repurchase the Ascend
Stock Option, either in whole or in part. In addition, Cascade has certain
rights under the Ascend Stock Option Agreement to "put" any or all shares
purchased under the Ascend Stock Option back to the Issuer. Under these stock
"put" provisions, Cascade has the right to require the Issuer to repurchase any
or all shares purchased by Cascade under the Ascend Stock Option. At the
Issuer's discretion, or as specified by Cascade, all or part of the share
repurchase price will be paid by redelivery of the shares of Cascade previously
issued to the Issuer as payment of the purchase price under the Ascend Stock
Option.

        After any exercise of the Ascend Stock Option by Cascade, the Issuer
would have certain "first refusal" rights with respect to the shares of Common
Stock acquired by Cascade under the Ascend Stock Option. Under these "first
refusal" rights, the Issuer has the right to repurchase all (but not less than
all) of Common Stock acquired by Cascade under the Ascend Stock Option.

        The aggregate amount payable by Issuer under the Ascend Stock Option
Agreement is capped, as are the aggregate net proceeds receivable by Cascade
from sales of shares received upon exercise of the Ascend Stock Option. The
maximum amount payable by the Issuer to Cascade under the Merger Agreement and
the "put" provisions of the Ascend Stock Option Agreement may not exceed $85
million. In addition, if Cascade would receive net proceeds of more than $85
million (over and above the aggregate
<PAGE>
 
- -----------------------                                  ---------------------
  CUSIP NO. 043491 10 9                                    PAGE 8 OF 14 PAGES
- -----------------------                                  ---------------------

exercise price) from third party sales or dispositions of the shares of Common
Stock acquired under the Ascend Stock Option, all net proceeds in excess of such
amount will be remitted to the Issuer.

        Under the Ascend Stock Option Agreement, Cascade's right to sell,
assign, pledge or otherwise dispose of or transfer shares of the Issuer is
subject to certain restrictions and first-refusal rights in favor of the Issuer.
In addition, the Ascend Stock Option Agreement gives Cascade certain rights to
have the shares acquired upon exercise of the Ascend Stock Option be registered
under the securities Act of 1933, as amended, for sale in a public offering. The
registration rights take effect after the termination of the Merger Agreement
and are subject to conditions and limitations. In lieu of registration, the
Ascend Stock Option Agreement gives the Issuer the option to agree to purchase,
for cash, all or part of the securities covered by the registration request, at
a price equal to the average last sale price of the Common Stock for the
preceding ten trading days. The Ascend Stock Option Agreement allows Cascade to
demand two registrations, and allows the Issuer to defer the requested
registrations for certain periods in the following circumstances: (i) for up to
40 days when the Issuer is in possession of material non-public information
which it reasonably believes is would be detrimental to be disclosed at such
time and which, in the opinion of counsel to the Issuer, would be required to be
disclosed in the registration statement, and (ii) for up to 90 days when
required audited financial statements are not yet available or the Issuer
reasonably determines that registration would interfere with a material
financing, acquisition or other transaction.

        The foregoing summary of the Ascend Stock Option is qualified in its
entirety by reference to the copy of the Ascend Stock Option Agreement included
as Exhibit 2 to this Schedule 13D and incorporated herein in its entirety by
   ---------
reference. If the Merger is consummated pursuant to the Merger Agreement, the
Ascend Stock Option will not be exercised.

        As an inducement to the Issuer to enter into the Merger Agreement,
Issuer and Cascade have also entered into a Cascade Stock Option Agreement, 
which entitles the Issuer to purchase up to 18,765,939 shares of Cascade Common
Stock under the circumstances specified in the Cascade Stock Option Agreement 
between Cascade and the Issuer. The foregoing summary of the Cascade Stock 
Option Agreement is qualified in its entirety by reference to the copy of the 
Cascade Stock Option Agreement included as Exhibit 1 to this Schedule 13D and
                                   ---------
incorporated herein in its entirety by reference. If the Merger is consummated
pursuant to the Merger Agreement, the Cascade Stock Option will not be
exercised.

        Also as an inducement to Issuer to enter into the Merger Agreement, 
the directors and executive officers (the "Voting Agreement Stockholders") of
Cascade have entered into a Cascade Director and Officer Stock Voting
Agreement (collectively the "Cascade Voting Agreements") with Issuer. Pursuant
to each Voting Agreement, the Voting Agreement Stockholders have agreed to
vote the shares of Cascade Common Stock owned by them (i) in favor of approval
and adoption of the Merger Agreement and the Merger and (ii) against approval
of any proposal made in opposition to or competition with consummation of the
Merger. The Voting Agreement Stockholders have also irrevocably appointed the
Issuer as their lawful attorney and proxy to vote the shares of Cascade Common
Stock owned by the Voting Agreement Stockholders in the manner described in
the previous sentence. The Voting Agreements each terminates upon the earlier
to occur of the Effective Time or the termination of the Merger Agreement. The
foregoing summary of each of the Cascade Voting Agreements is qualified in its
entirety by reference to the copy of the form of Cascade Voting Agreement
included as Exhibit 3 of this Schedule 13D and incorporated herein in its
entirety by reference. Inasmuch as the Issuer's voting rights under the Voting
Agreements are limited solely to certain matters related to the Merger, and
the Issuer has no economic interest in or dispositive power over the shares of
the Issuer's Common Stock covered thereby, and such shares may be sold by the
holders thereof, the
<PAGE>
 
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  CUSIP NO. 043491 10 9                                   PAGE 9 OF 14 PAGES
- -----------------------                                  ---------------------

Issuer expressly disclaims beneficial ownership of the shares of Common Stock of
the Issuer covered by the Cascade Voting Agreements. As an inducement to Cascade
to enter into the Merger Agreement, all of the directors and executive officers
of the Issuer have entered into an Ascend Director and Officer Stock Voting
Agreement dated as of March 30, 1997 with the Issuer, the substance of which is
substantially similar to the substance of the Cascade Voting Agreements. A copy
of the form of Ascend Director and Officer Stock Voting Agreement is included as
Exhibit 4 of this Schedule 13D and incorporated herein in its entirety by
- ---------
reference.

        Also in connection with the Merger Agreement, the Voting Agreement
Stockholders and the directors and executive officers of Cascade have each
entered into a Director, Officer and Stockholder Agreement with Ascend
(collectively, the "Agreements") pursuant to which each person has agreed not to
sell, exchange, transfer, pledge, dispose or otherwise reduce its risk relative
to any shares of Issuer Common Stock or other equity securities of Issuer (and
Cascade Common Stock with respect to its directors and executive officers) owned
by it during the period beginning on the date 30 days prior to the Closing Date
(as defined in the Merger Agreement) and ending on the day after Ascend has
published financial results covering at least 30 days of combined operations of
Ascend and Cascade in the form of a quarterly earnings report, an effective
registration statement filed with the Securities and Exchange Commission
("Commission"), a report to the Commission on Form 10-K, 10-Q or 8-K, or any
other public filing or announcement which includes the combined results of
operations. The foregoing summary of the Agreements is qualified in its entirety
by reference to the forms of the Agreements included as Exhibits 5 and 6 of this
                                                        ----------------
Schedule 13D and incorporated herein in its entirety by reference.

        Upon consummation of the Merger, the Certificate of Incorporation of the
Issuer, as in effect immediately prior to the Merger, shall be the Certificate
of Incorporation of the Issuer until thereafter amended.

        Other than as described above, Cascade currently has no plan or
proposals which relate to, or may result in, any of the matters listed in Items
4(a) - (j) of Schedule 13D (although Cascade reserves the right to develop such
plans).

ITEM 5.  INTEREST IN SECURITIES OF THE ISSUER

        As a result of the Ascend Voting Agreements, Cascade has sole power to
vote an aggregate of 6,608,172 shares of Issuer Common Stock for the limited
purposes described in Item 4 above, and such shares constitute approximately 
5.3% of the issued and outstanding shares of Issuer Common Stock as of March
24, 1997.

        If the Ascend Stock Option is exercised, Cascade will have the right to
acquire 24,025,741 shares of Issuer Common Stock. If acquired, Cascade would
have sole voting and dispositive power over such shares, and such shares would
constitute approximately 16.6% of the issued and outstanding shares of the 
Issuer Common Stock as of March 24, 1997.

        To Cascade's knowledge, no shares of Issuer Common Stock are
beneficially owned by any of the persons named in Schedule A, except for
245,011 shares held by Matrix Partners III, L.P., of which Matrix III 
Management Company is a general partner of which Paul J. Ferri, a current 
director of Cascade, is a general partner.

        Neither Cascade, nor, to Cascade's knowledge, any person named in
Schedule A, has affected any transaction in the Issuer Common Stock during the
past 60 days, except for 245,011 shares
<PAGE>
 
- -----------------------                                  ---------------------
  CUSIP NO. 043491 10 9                                   PAGE 10 OF 14 PAGES
- -----------------------                                  ---------------------

acquired by Matrix Partners III, L.P., of which Matrix III Management Company 
is a general partner of which Paul J. Ferri, a current director of Cascade, is
a general partner, upon the consummation of a merger of a wholly-owned
subsidiary of Issuer with and into Whitetree, Inc.

ITEM 6.  CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS
         WITH RESPECT TO SECURITIES OF THE ISSUER

        Other than as described herein, to Cascade's knowledge, there are no
contracts, arrangements, understandings or relationships (legal or otherwise)
among the persons named in Item 2 and between such persons and any person with
respect to any securities of the Issuer, including but not limited to transfer
or voting of any of the securities, finder's fees, joint ventures, loan or
option arrangements, puts or calls, guarantees of profits, division of profits
or loss, or the giving or withholding of proxies.

ITEM 7.  MATERIAL TO BE FILED AS EXHIBITS


        Exhibit No.                     Description
 
           1                 Cascade Stock Option Agreement dated March 30,
                             1997, by and between Ascend Communications, Inc., a
                             Delaware corporation, and Cascade Communications
                             Corp., a Delaware corporation

           2                 Form of Ascend Stock Option Agreement dated 
                             March 30, 1997, by and among Ascend 
                             Communications, Inc., a Delaware corporation, 
                             and Cascade Communications Corp.,
                             a Delaware corporation

           3                 Form of Cascade Director and Officer Stock Voting
                             Agreement dated as of March 30, 1997, by and among
                             Ascend Communications, Inc., a Delaware 
                             corporation and all directors and executive 
                             officers of Cascade Communications Corp., a 
                             Delaware corporation

           4                 Form of Ascend Director and Officer Stock Voting 
                             Agreement dated as of March 30, 1997, by and among
                             Cascade Communications Corp.., a Delaware 
                             corporation and all directors and executive 
                             officers of Ascend Communications, Inc., a 
                             Delaware corporation

           5                 Form of Cascade Director, Officer and Stockholder 
                             Agreement dated as of March 30, 1997

           6                 Form of Ascend Director, Officer and Stockholder 
                             Agreement dated as of March 30, 1997
<PAGE>
 
- -----------------------                                  ---------------------
  CUSIP NO. 043491 10 9                                   PAGE 11 OF 14 PAGES
- -----------------------                                  ---------------------

                                   SIGNATURE

        After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


Date:  April 9, 1997                    CASCADE COMMUNICATIONS CORP.



                                        By: /s/ Paul E. Blondin
                                            ------------------------
                                            Paul E. Blondin
                                            Chief Financial Officer
<PAGE>
 
- -----------------------                                  ---------------------
  CUSIP NO. 043491 10 9                                   PAGE 12 OF 14 PAGES
- -----------------------                                  ---------------------


                                  SCHEDULE A
<TABLE> 
<CAPTION> 

                                                         Name and Address of Corporation
                         Principal Occupation                or Other Organization in
Name                        or Employment                        Which Employed
- ----                        -------------                        --------------
<S>                     <C>                                   <C> 

Victoria A. Brown        President                              Communicore
                                                                PO Box 749
                                                                Stuart, FL  34995

Richard M. Burnes, Jr.   General Partner                        The Charles River Partnerships
                                                                1000 Winter Street, Suite 3300
                                                                Waltham, MA  02154

Gururaj Deshpande        Chairman of the Board of Directors,    Cascade Communications Corp.
                         Executive Vice President of Business   5 Carlisle Road
                         Development                            Westford, MA  01886

Paul J. Ferri            General Partner                        Matrix Partners
                                                                Bay Colony Corporate Center
                                                                1000 Winter Street, Suite 4500
                                                                Waltham, MA 02154

Bruns H. Grayson        Managing General Partner                Calvert Capital L.P.
                                                                One South Street, Suite 2150
                                                                Baltimore, MD  21202

Daniel E. Smith         President, Chief Executive Officer      Cascade Communications Corp.
                                                                5 Carlisle Road
                                                                Westford, MA  01886

Steven C. Walske        Chief Executive Officer                 Parametric Technology Corporation
                                                                128 Technology Drive
                                                                Waltham, MA  02154

Hassan M. Ahmed         Vice President of Engineering           Cascade Communications Corp.
                                                                5 Carlisle Road
                                                                Westford, MA  01886

Paul E. Blondin         Vice President of Finance and           Cascade Communications Corp.
                        Administration, Chief Financial         5 Carlisle Road
                        Officer                                 Westford, MA  01886

Michael A. Champa       Vice President of Worldwide Sales       Cascade Communications Corp.
                        and Customer Service                    5 Carlisle Road
                                                                Westford, MA  01886

James A. Dolce, Jr.     Vice President and General Manager of   Cascade Communications Corp.
                        Remote Access                           5 Carlisle Road
                                                                Westford, MA  01886

John E. Dowling         Vice President of Operations            Cascade Communications Corp.
                                                                5 Carlisle Road
                                                                Westford, MA  01886

Robert N. Machlin       Vice President of Marketing             Cascade Communications Corp.
                                                                5 Carlisle Road
                                                                Westford, MA  01886

Jonathan M. Reeves      Vice President and General Manager      Cascade Communications Corp.
                        of Broadband Access                     5 Carlisle Road
                                                                Westford, MA  01886
</TABLE>
<PAGE>
 
- -----------------------                                  ---------------------
  CUSIP NO. 043491 10 9                                   PAGE 13 OF 14 PAGES
- -----------------------                                  ---------------------

                                  SCHEDULE B

<TABLE> 
<CAPTION> 

                                                                      
                                Number of Shares of Issuer            
Individual                    Common Stock Beneficially Owned         
- ----------                    -------------------------------         
<S>                           <C>   
Mory Ejabat                             1,416,729

Curtis N. Sanford                         633,501

Robert K. Dahl                            859,920

Michael Hendren                           475,841

Anthony Stagno                            137,132

Michael J. Johnson                        127,258

Jeanette Symons                         1,073,765

Bernard Schneider                         254,167

William H. Kind                           206,250

Maureen Lawrence                                0

Betsy S. Atkins                            95,504

Roger L. Evans                          1,018,279

C. Richard Kramlich                       166,618

James P. Lally                            141,608

Martin Schoffstall                          1,600

                                        
</TABLE> 
<PAGE>
 
- -----------------------                                  ---------------------
  CUSIP NO.  043491 10 9                                  PAGE 14 OF 14 PAGES
- -----------------------                                  ---------------------


        Exhibit No.                     Description

           1               Cascade Stock Option Agreement dated March 30, 1997,
                           by and between Ascend Communications, Inc., a
                           Delaware corporation, and Cascade Communications
                           Corp., a Delaware corporation

           2               Ascend Stock Option Agreement dated March 30, 1997,
                           by and among Ascend Communications, Inc., a Delaware
                           corporation, and Cascade Communications Corp., a
                           Delaware corporation

           3               Form of Cascade Director and Officer Stock Voting
                           Agreement dated as of March 30, 1997, by and among
                           Ascend Communications, Inc., a Delaware corporation
                           and all directors and executive officers of Cascade
                           Communications Corp., a Delaware corporation

           4               Form of Ascend Director and Officer Stock Voting
                           Agreement dated as of March 30, 1997, by and among
                           Cascade Communications Corp., a Delaware
                           corporation and all directors and executive
                           officers of Ascend Communications, Inc., a Delaware
                           corporation

           5               Form of Cascade Director, Officer and Stockholder
                           Agreement dated as of March 30, 1997

           6               Form of Ascend Director, Officer and Stockholder
                           Agreement dated as of March 30, 1997

<PAGE>
 
                                                                      EXHIBIT 1
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
                         CASCADE STOCK OPTION AGREEMENT
 
                                 BY AND BETWEEN
 
                         CASCADE COMMUNICATIONS CORP.,
                            A DELAWARE CORPORATION,
 
                                      AND
 
                          ASCEND COMMUNICATIONS, INC.,
                            A DELAWARE CORPORATION,
 
 
 
                           DATED AS OF MARCH 30, 1997
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
 
                             TABLE OF DEFINED TERMS
 
<TABLE>
<CAPTION>
TERM                                                                   SECTION
- ----                                                                   --------
<S>                                                                    <C>
Agreement............................................................. Preamble
Ascend................................................................ Preamble
Ascend Common Stock................................................... 2(e)
Ascend Offer Notice................................................... 8(c)
Cash Exercise......................................................... 2(e)
Cash Exercise Price................................................... 2(e)
Cascade............................................................... Preamble
Cascade Charter....................................................... 2(b)
Cascade Common Stock.................................................. Recitals
Cascade Offer Notice.................................................. 8(d)
Cascade Option........................................................ 1
Closing............................................................... 2(b)
Exercise Notice....................................................... 2(b)
Exercise Price........................................................ 2(e)
Expiration Date....................................................... 8(a)
Fair Market Value..................................................... 7(b)(iii)
Holder................................................................ 9(a)
Holder's Designation Notice........................................... 9(b)
HSR Act............................................................... 3
Manager............................................................... 9(b)
Material Contract..................................................... 5(e)
Merger................................................................ Recitals
Merger Agreement...................................................... Recitals
Net Proceeds.......................................................... 2(f)
Option Number......................................................... 2(d)
Option Repurchase Price............................................... 7(b)(i)
Permitted Offering.................................................... 9(a)
Purchase Period....................................................... 7(a)
Registrable Securities................................................ 9(a)
Registrant............................................................ 9(a)
Registrant's Designation Notice....................................... 9(b)
Registration Notice................................................... 9(a)
Repurchase Notice..................................................... 7(a)
Restricted Shares..................................................... 8(a)
Share Repurchase Price................................................ 7(b)(ii)
Stock Exercise........................................................ 2(e)
Stock Exercise Price.................................................. 2(e)
Sub................................................................... Recitals
Trigger Event......................................................... 2(a)
Violation............................................................. 5(e)
</TABLE>
 
                                       i
<PAGE>
 
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                                            PAGE
                                                                            ----
 <C>     <C>  <S>                                                           <C>
 Section 1.   Grant of Option.............................................   B-1
 Section 2.   Exercise and Termination of the Cascade Option..............   B-1
         (a)  Exercise....................................................   B-1
         (b)  Exercise Procedure..........................................   B-1
         (c)  Termination of the Cascade Option...........................   B-2
         (d)  Option Number...............................................   B-2
         (e)  Exercise Price..............................................   B-2
         (f)  Certain Limitations.........................................   B-2
 Section 3.   Conditions to Closing.......................................   B-3
 Section 4.   Closing.....................................................   B-3
 Section 5.   Representations and Warranties of Cascade...................   B-3
         (a)  Organization and Standing...................................   B-3
         (b)  Authority...................................................   B-3
         (c)  Reservation of Shares.......................................   B-4
         (d)  No Liens....................................................   B-4
         (e)  No Conflicts................................................   B-4
         (f)  Consents and Approvals......................................   B-4
         (g)  Investment Purposes.........................................   B-4
 Section 6.   Representations and Warranties of Ascend....................   B-4
         (a)  Organization and Standing...................................   B-4
         (b)  Authority...................................................   B-4
         (c)  Reservation of Shares.......................................   B-5
         (d)  No Liens....................................................   B-5
         (e)  No Conflicts................................................   B-5
         (f)  Consents and Approvals......................................   B-5
         (g)  Investment Purpose..........................................   B-5
 Section 7.   Certain Repurchases.........................................   B-5
         (a)  Ascend "Put"................................................   B-5
         (b)  Certain Definitions.........................................   B-6
         (c)  Redelivery of Shares of Ascend Common Stock.................   B-6
         (d)  Payment and Redelivery of Cascade Options or Shares.........   B-6
         (e)  Repurchase Price Reduced at Ascend's Option.................   B-6
 Section 8.   Restrictions on Transfer....................................   B-6
         (a)  Restrictions on Transfer....................................   B-6
         (b)  Permitted Sales.............................................   B-7
         (c)  Cascade's Right of First Refusal............................   B-7
         (d)  Ascend's Right of First Refusal.............................   B-7
         (e)  Additional Restrictions.....................................   B-8
 Section 9.   Registration Rights.........................................   B-8
         (a)  Procedure...................................................   B-8
         (b)  Manager's Certificate.......................................   B-8
         (c)  First Refusal Right.........................................   B-9
         (d)  Closing.....................................................   B-9
         (e)  Certain Limitations.........................................   B-9
         (f)  State Securities Laws.......................................   B-9
         (g)  Obligations of Registrant...................................   B-9
         (h)  Indemnification.............................................   B-9
         (i)  Inclusion of Additional Shares of Registrant................  B-10
</TABLE>
 
                                       ii
<PAGE>
 
<TABLE>
<CAPTION>
                                                                          PAGE
                                                                          ----
 <C>   <C>   <S>                                                          <C>
 Section 10. Adjustment Upon Changes in Capitalization..................  B-10
 Section 11. Restrictive Legends........................................  B-10
             Binding Effect; No Assignment; No Third-Party
 Section 12.  Beneficiaries.............................................  B-11
 Section 13. Specific Performance.......................................  B-11
 Section 14. Validity...................................................  B-11
 Section 15. Notices....................................................  B-12
 Section 16. Governing Law..............................................  B-12
 Section 17. Interpretation.............................................  B-12
 Section 18. Counterparts; Effect.......................................  B-13
 Section 19. Expenses...................................................  B-13
 Section 20. Amendments; Waiver.........................................  B-13
 Section 21. Extension of Time Periods..................................  B-13
 Section 22. Further Assurances.........................................  B-13
</TABLE>
 
                                      iii
<PAGE>
 
                        CASCADE STOCK OPTION AGREEMENT
 
  THIS CASCADE STOCK OPTION AGREEMENT (the "Agreement") is made and entered
into as of March 30, 1997 by and between Cascade Communications Corp., a
Delaware corporation ("Cascade"), and Ascend Communications, Inc., a Delaware
corporation ("Ascend").
 
                                   Recitals
 
  Concurrently with the execution and delivery of this Agreement, Cascade,
Ascend, and Catskill Merger Corporation, a Delaware corporation and a wholly-
owned subsidiary of Ascend ("Sub"), are entering into an Agreement and Plan of
Reorganization, dated as of March 30, 1997 (the "Merger Agreement"), which
provides for the merger of Sub with and into Cascade in accordance with the
terms of the Merger Agreement and the laws of the State of Delaware (the
"Merger"). As a condition and inducement to Ascend's willingness to enter into
the Merger Agreement, Ascend has requested that Cascade agree, and Cascade has
agreed, to grant to Ascend an option to acquire certain shares of Cascade's
authorized but unissued common stock, par value $.001 per share (together with
any associated rights, "Cascade Common Stock"), on the terms and subject to
the conditions set forth herein.
 
  NOW, THEREFORE, to induce Ascend to enter into the Merger Agreement and in
consideration of the representations, warranties, covenants and agreements
contained herein and in the Merger Agreement, the parties hereto, intending to
be legally bound, hereby agree as follows. Capitalized terms used herein but
not defined herein shall have the meanings ascribed to them in the Merger
Agreement.
 
                                   Agreement
 
  Section 1. Grant of Option. Cascade hereby grants to Ascend an irrevocable
option (the "Cascade Option") to purchase a number of shares of Cascade Common
Stock equal to the Option Number (as defined in Section 2(d)), on the terms
and subject to the conditions set forth below.
 
  Section 2. Exercise and Termination of the Cascade Option.
 
  (a) Exercise. The Cascade Option may be exercised by Ascend, in whole or in
part, at any time or from time to time prior to the termination of Ascend's
right to exercise the Cascade Option by the terms of this Agreement and upon and
after the occurrence of the earliest event which causes (i) the Cascade
Termination Fee or (ii) the Cascade Post-Termination Fee (in each case as
defined in the Merger Agreement) to become payable (a "Trigger Event").
Notwithstanding the foregoing, the Cascade Option may not be exercised if Ascend
is in breach in any material respect of any of its material representations,
warranties, covenants or agreements contained in this Agreement or the Merger
Agreement.
 
  (b) Exercise Procedure. In the event that Ascend wishes to exercise the
Cascade Option, Ascend shall deliver to Cascade written notice (an "Exercise
Notice") specifying the total number of shares of Cascade Common Stock that
Ascend wishes to purchase. To the extent permitted by law and the Certificate
of Incorporation, as amended, of Cascade (the "Cascade Charter"), and provided
that the conditions set forth in Section 3 to Cascade's obligation to issue
the shares of Cascade Common Stock to Ascend hereunder have been satisfied or
waived, Ascend shall, upon delivery of the Exercise Notice and tender of the
applicable aggregate Exercise Price, immediately be deemed to be the holder of
record of the shares of Cascade Common Stock issuable upon such exercise,
notwithstanding that the stock transfer books of Cascade shall then be closed
or that certificates representing such shares of Cascade Common Stock shall
not theretofore have been delivered to Ascend. Each closing of a purchase of
shares of Cascade Common Stock hereunder (a "Closing") shall occur at a place,
on a date, and at a time designated by Ascend in an Exercise Notice delivered
at least two (2) business days prior to the date of such Closing.
 
                                      B-1
<PAGE>
 
  (c) Termination of the Cascade Option. Ascend's right to exercise the
Cascade Option shall terminate upon the earliest to occur of:
 
    (i) the Effective Time of the Merger;
 
    (ii) the date on which the Merger Agreement is terminated pursuant to
  Article VIII thereof other than under circumstances which also constitute a
  Trigger Event under this Agreement; and
 
    (iii) (A) in the event the Cascade Option becomes exercisable pursuant to
  clause (i) of Section 2(a), the date two hundred seventy (270) days after the
  date on which the Merger Agreement is terminated pursuant to Article VIII
  thereof under circumstances which also constitute a Trigger Event under clause
  (i) of Section 2(a), or
 
    (B) in the event the Cascade Option becomes exercisable pursuant to clause
  (ii) of Section 2(a), the later of (I) the date two hundred seventy (270) days
  after the date on which the Merger Agreement is terminated pursuant to Article
  VIII thereof under circumstances which also constitute a Trigger Event under
  clause (ii) of Section 2(a) and (II) the date one hundred eighty (180) days
  after the date on which the Cascade Option becomes exercisable pursuant to
  clause (ii) of Section 2(a).
 
Notwithstanding the foregoing, with respect to clause (iii) in the immediately
preceding sentence, if the Cascade Option cannot be exercised by reason of any
applicable judicial or governmental judgment, decree, order, law or regulation,
the Cascade Option shall remain exercisable and shall not terminate until the
earlier of (x) the date on which such impediment shall become final and not
subject to appeal and (y) 5:00 p.m., Pacific Standard Time, on the tenth (10th)
business day after such impediment shall have been removed; provided, however,
that if such judgment, decree, or order shall have been obtained at the request
of Cascade or any of its Affiliates or a party that has made or is proposing to
make a Competing Offer (as such term is defined in the Merger Agreement) for
Cascade, and such judgment, decree or order is vacated, set aside, withdrawn,
reversed or otherwise nullified, the time during which the Cascade Option shall
remain exercisable shall be extended for as long as such judgment, decree, or
order shall be in effect. The rights of Ascend set forth in Sections 7 and 9
shall not terminate upon termination of Ascend's right to exercise the Cascade
Option with respect to shares acquired prior to such termination, but shall
extend to the time provided in such sections. Notwithstanding the termination of
the Cascade Option, Ascend shall be entitled to purchase the shares of Cascade
Common Stock with respect to which Ascend had exercised the Cascade Option prior
to such termination.
 
  (d) Option Number. The aggregate number of shares of Cascade Common Stock
issuable upon exercise of this Cascade Option (the "Option Number") shall
initially be the number of shares, rounded down to the nearest whole share,
equal to nineteen and nine-tenths percent (19.9%) of the total number of
shares of Cascade Common Stock issued and outstanding as of the date of this
Agreement, and shall be adjusted hereafter to reflect changes in Cascade's
capitalization occurring after the date hereof in accordance with Section 10.
Notwithstanding any other provision of this Agreement, in no event shall the
Option Number exceed nineteen and nine-tenths percent (19.9%) of the total
number of shares of Cascade Common Stock issued and outstanding as of the date
of this Agreement, adjusted in accordance with Section 10.
 
  (e) Exercise Price. The purchase price per share of Cascade Common Stock
pursuant to the Cascade Option (the "Exercise Price") shall be payable, at
Ascend's election, in cash (a "Cash Exercise") or in shares (a "Stock
Exercise") of Ascend common stock, $.001 par value per share ("Ascend Common
Stock"). The Exercise Price per share of Cascade Common Stock, (i) in the case
of a Cash Exercise, shall be a cash amount equal to $36.40 (the "Cash Exercise
Price"), and (ii) in the case of a Stock Exercise, shall be seven tenths (.7) of
a share of Ascend Common Stock (the "Stock Exercise Price").
 
  (f) Certain Limitations. In the event Ascend would receive aggregate,
cumulative Net Proceeds (as defined below) of more than eighty-five million
dollars ($85,000,000) in connection with the sale (or other disposition) to
any third party of the shares of Cascade Common Stock acquired pursuant to the
Cascade Option (other than a sale of such shares pursuant to Section 7), all
Net Proceeds in excess of such amount shall be remitted to Cascade promptly
upon receipt. "Net Proceeds" shall mean the aggregate proceeds of such sale or
disposition in excess of the product of the Exercise Price multiplied by the
number of shares of Cascade Common
 
                                      B-2
<PAGE>
 
Stock included in such sale or disposition. Notwithstanding anything in this
Agreement or in the Merger Agreement to the contrary, the maximum aggregate
amount payable by Cascade to Ascend and its affiliates pursuant to Section 7
of this Agreement and the provisions of Section 8.3(b) of the Merger Agreement
shall not exceed the sum of eighty-five million dollars ($85,000,000) plus, in
the case of payments pursuant to Sections 7(a)(ii) and 7(b)(ii) of this
Agreement, the aggregate Exercise Price for the shares of Cascade Common Stock
repurchased by Cascade from Ascend pursuant to Section 7 of this Agreement, it
being understood that the limitation contained in this sentence shall not
limit the amounts receivable by Ascend from persons other than Cascade,
including without limitation amounts receivable pursuant to a tender offer or
other purchase and sale transaction.
 
  Section 3. Conditions to Closing. The obligation of Cascade to issue the
shares of Cascade Common Stock to Ascend hereunder is subject to the
conditions that (a) all waiting periods, if any, under the Hart Scott Rodino
Antitrust Improvements Act of 1975, as amended (the "HSR Act"), applicable to
the issuance of the shares of Cascade Common Stock by Cascade and the
acquisition of such shares by Ascend hereunder (and, in the case of a Stock
Exercise, the issuance of shares of Ascend Common Stock by Ascend and the
acquisition of such shares by Cascade) shall have expired or have been
terminated; (b) no preliminary or permanent injunction or other order by any
court of competent jurisdiction prohibiting or otherwise restraining such
issuance shall be in effect; and (c) all consents, approvals, orders,
authorizations and permits of any federal, state, local or foreign
governmental authority, if any, required in connection with the issuance of
the shares of Cascade Common Stock and the acquisition of such shares by
Ascend hereunder (and, in the case of a Stock Exercise, the issuance of shares
of Ascend Common Stock and the acquisition of such shares by Cascade) shall
have been obtained.
 
  Section 4. Closing. At any Closing: (a) Cascade shall deliver to Ascend or
its designee a single certificate in definitive form representing the number
of shares of Cascade Common Stock designated by Ascend in its Exercise Notice,
such certificate to be registered in the name of Ascend and to bear the legend
set forth in Section 11; and (b) Ascend shall deliver to Cascade the aggregate
Exercise Price for the shares of Cascade Common Stock so designated and being
purchased by (i) wire transfer of immediately available funds to the account
or accounts specified in writing by Cascade (in the case of a Cash Exercise),
or (ii) subject to the satisfaction of applicable conditions, delivery of a
certificate or certificates representing the number of shares of Ascend Common
Stock being issued by Ascend in consideration thereof (in the case of a Stock
Exercise). Effective at or prior to the Closing, Cascade shall cause the
shares of Cascade Common Stock being delivered at the Closing to be approved
for quotation on The Nasdaq National Market, and Ascend shall cause the shares
of Ascend Common Stock being delivered at the Closing pursuant to a Stock
Exercise to be approved for quotation on The Nasdaq National Market.
 
  Section 5. Representations and Warranties of Cascade. Cascade represents and
warrants to Ascend as follows:
 
    (a) Organization and Standing. Cascade is a corporation duly organized,
  validly existing and in good standing under the laws of the State of
  Delaware and has all corporate power and authority required to enter into
  this Agreement and to carry out its obligations hereunder.
 
    (b) Authority. The execution and delivery of this Agreement by Cascade
  and the consummation by Cascade of the transactions contemplated hereby
  have been duly authorized by all necessary corporate action on the part of
  Cascade and no other corporate proceedings on the part of Cascade and no
  action of Cascade shareholders are necessary to authorize this Agreement or
  any of the transactions contemplated hereby; this Agreement has been duly
  and validly executed and delivered by Cascade and, assuming the due
  authorization, execution and delivery hereof by Ascend and the receipt of
  all required governmental approvals, constitutes the valid and binding
  obligation of Cascade, enforceable against Cascade in accordance with its
  terms, except as may be limited by applicable bankruptcy, insolvency,
  reorganization or other similar laws affecting the enforcement of
  creditors' rights generally, and except that the availability of equitable
  remedies, including specific performance, may be subject to the discretion
  of any court before which any proceeding therefor may be brought.
 
 
                                      B-3
<PAGE>
 
    (c) Reservation of Shares. Cascade has taken all necessary corporate
  action to authorize and reserve for issuance and to permit it to issue,
  upon exercise of the Cascade Option, and at all times from the date hereof
  through the expiration of the Cascade Option will have reserved, a number
  of authorized and unissued shares of Cascade Common Stock not less than the
  Option Number, such amount being subject to adjustment as provided in
  Section 10, all of which, upon their issuance and delivery in accordance
  with the terms of this Agreement, will be duly authorized, validly issued,
  fully paid and nonassessable.
 
    (d) No Liens. The shares of Cascade Common Stock issued to Ascend upon
  the exercise of the Cascade Option will be, upon delivery thereof to
  Ascend, free and clear of all claims, liens, charges, encumbrances and
  security interests of any nature whatsoever.
 
    (e) No Conflicts. The execution and delivery of this Agreement by Cascade
  does not, and, subject to compliance with applicable law, the consummation
  by Cascade of the transactions contemplated hereby will not, violate,
  conflict with, or result in a breach of any provision of, or constitute a
  default (with or without notice or lapse of time, or both) under, or result
  in the termination of, or accelerate the performance required by, or result
  in a right of termination, cancellation, or acceleration of any obligation
  or the loss of a material benefit under, or the creation of a lien, pledge,
  security interest or other encumbrance on assets (any such violation,
  conflict, breach, default, termination, acceleration, right of termination,
  cancellation or acceleration, loss, or creation, a "Violation") by Cascade
  or any of its Subsidiaries of (i) any provision of the charter or the
  Bylaws of Cascade or any of its Subsidiaries, each as amended to date, (ii)
  any material provision of any material loan or credit agreement, note,
  mortgage, indenture, lease, benefit plan or other agreement, obligation,
  instrument, permit, concession, franchise or license (a "Material
  Contract") of Cascade or any of its Subsidiaries or to which any of them is
  a party or by which any of them or their properties or assets are bound, or
  (iii) except as contemplated by Section 3.4(c) of the Merger Agreement or
  Section 5(f) below, any judgment, order, decree, statute, law, ordinance,
  rule or regulation applicable to Cascade or any of its subsidiaries or any
  of their properties or assets.
 
    (f) Consents and Approvals. The execution and delivery of this Agreement
  by Cascade does not, and (except for the notifications required under the
  HSR Act and applicable foreign laws, the expiration or early termination of
  waiting periods under the HSR Act and applicable foreign laws, and the
  receipt of approvals under applicable securities laws, and except as
  contemplated by Section 9) the performance of this Agreement by Cascade and
  the consummation of the transactions contemplated hereby will not, require
  any consent, approval, order, authorization or permit of, filing with, or
  notification to any governmental or regulatory authority, other than such
  consents, approvals, orders, authorizations, permits, filings and
  notifications which, in the aggregate, if not obtained or made, could not
  reasonably be expected to have a Cascade Material Adverse Effect or an
  Ascend Material Adverse Effect (as such terms are defined in the Merger
  Agreement) or a material adverse effect on the ability of the parties to
  consummate the transactions contemplated by this Agreement.
 
    (g) Investment Purposes. Any shares of Ascend Common Stock acquired by
  Cascade pursuant to this Agreement will be acquired for Cascade's own
  account, for investment purposes only, and will not be acquired by Cascade
  with a view to the public distribution thereof in violation of any
  applicable provision of the Securities Act.
 
  Section 6. Representations and Warranties of Ascend. Ascend represents and
warrants to Cascade as follows:
 
    (a) Organization and Standing. Ascend is a corporation duly organized,
  validly existing and in good standing under the laws of the State of
  Delaware and has all corporate power and authority required to enter into
  this Agreement and to carry out its obligations hereunder.
 
    (b) Authority. Except as set forth in Section 6(c), the execution and
  delivery of this Agreement by Ascend and the consummation by Ascend of the
  transactions contemplated hereby have been duly authorized by all necessary
  corporate action on the part of Ascend, and no other corporate proceedings
  on the part of Ascend and no action of its stockholders are necessary to
  authorize this Agreement or any of the transactions contemplated hereby;
  this Agreement has been duly and validly executed and delivered by
 
                                      B-4
<PAGE>
 
  Ascend and, assuming the due authorization, execution and delivery hereof
  by Cascade and the receipt of all required governmental approvals,
  constitutes the valid and binding obligation of Ascend, enforceable against
  Ascend in accordance with its terms, except as may be limited by applicable
  bankruptcy, insolvency, reorganization, or other similar laws affecting the
  enforcement of creditors' rights generally, and except that the
  availability of equitable remedies, including specific performance, may be
  subject to the discretion of any court before which any proceeding may be
  brought.
 
    (c) Reservation of Shares. Prior to any delivery of shares of Ascend
  Common Stock in consideration of the purchase of shares of Cascade Common
  Stock pursuant hereto, Ascend will have taken all necessary corporate
  action to authorize for issuance and to permit it to issue such shares of
  Ascend Common Stock, all of which, upon their issuance and delivery in
  accordance with the terms of this Agreement, will be duly authorized,
  validly issued, fully paid and nonassessable.
 
    (d) No Liens. The shares of Ascend Common Stock (if any) issued to
  Cascade in consideration of the purchase of shares of Cascade Common Stock
  pursuant hereto will be, upon delivery thereof to Cascade, free and clear
  of all claims, liens, charges, encumbrances and security interests of any
  nature whatsoever.
 
    (e) No Conflicts. The execution and delivery of this Agreement by Ascend
  does not, and the consummation by Ascend of the transactions contemplated
  hereby will not, violate, conflict with, or result in a Violation by Ascend
  or any of its Subsidiaries, of (i) any provision of the Certificate of
  Incorporation or Bylaws of Ascend, (ii) any material provision of any
  Material Contract of Ascend or any of its Subsidiaries or to which any of
  them is a party or by which any of them or their properties or assets are
  bound, or (iii) except as contemplated by Section 4.4(c) of the Merger
  Agreement or Section 6(f) below, any judgment, order, decree, statute, law,
  ordinance, rule or regulation applicable to Ascend or any of its
  subsidiaries or any of their properties or assets.
 
    (f) Consents and Approvals. The execution and delivery of this Agreement
  by Ascend does not, and (except for the notifications required under the
  HSR Act and applicable foreign laws, the expiration or early termination of
  any waiting periods under the HSR Act and applicable foreign laws, and the
  receipt of approvals under applicable securities laws, and except as
  contemplated by Section 9) the performance of this Agreement by Ascend and
  the consummation of the transactions contemplated hereby will not, require
  any consent, approval, order, authorization or permit of, filing with, or
  notification to any governmental or regulatory authority, other than such
  consents, approvals, orders, authorizations, permits, filings and
  notifications which, in the aggregate, if not obtained or made, could not
  reasonably be expected to have a Cascade Material Adverse Effect or an
  Ascend Material Adverse Effect (as such terms are defined in the Merger
  Agreement) or a material adverse effect on the ability of the parties to
  consummate the transactions contemplated by this Agreement.
 
    (g) Investment Purpose. Any shares of Cascade Common Stock acquired by
  Ascend upon exercise of the Cascade Option will be acquired for Ascend's
  own account, for investment purposes only and will not be, and the Cascade
  Option is not being, acquired by Ascend with a view to the public
  distribution thereof in violation of any applicable provision of the
  Securities Act.
 
  Section 7. Certain Repurchases.
 
  (a) Ascend "Put". At any time during which the Cascade Option is exercisable
pursuant to Section 2 (the "Purchase Period"), upon written notice to Cascade
by Ascend (the "Repurchase Notice"):
 
    (i) Cascade and its successors in interest shall repurchase from Ascend
  all or any portion of the Cascade Option, as specified by Ascend, to the
  extent not previously exercised, at the Option Repurchase Price set forth
  in Section 7(b)(i), subject to and as limited by Section 2(f) above; and
 
    (ii) Cascade and its successors in interest shall repurchase from Ascend
  all or any portion of the shares of Cascade Common Stock purchased by
  Ascend pursuant to the Cascade Option, as specified by Ascend, at the Share
  Repurchase Price set forth in Section 7(b)(ii) subject to and as limited by
  Section 2(f) above.
 
                                      B-5
<PAGE>
 
  (b) Certain Definitions. For purposes of this Section 7, the following
definitions shall apply:
 
    (i) Option Repurchase Price. "Option Repurchase Price" shall mean (A) the
  amount (if any) by which the Fair Market Value (as defined in Section
  7(b)(iii)) of a single share of Cascade Common Stock as of the date of the
  applicable Repurchase Notice exceeds the per share Exercise Price,
  multiplied by (B) the number of shares of Cascade Common Stock purchasable
  pursuant to the Cascade Option or the portion thereof covered by the
  applicable Repurchase Notice.
 
    (ii) Share Repurchase Price. "Share Repurchase Price" shall mean the
  product of (A) the greater of (I) the Exercise Price paid by Ascend per
  share of Cascade Common Stock acquired pursuant to the Cascade Option and
  (II) the Fair Market Value (as defined in Section 7(b)(iii)) of a single
  share of Cascade Common Stock as of the date of the applicable Repurchase
  Notice, and (B) the number of shares of Cascade Common Stock to be
  repurchased pursuant to this Section 7 as covered by the applicable
  Repurchase Notice.
 
    (iii) Fair Market Value. As used in this Agreement, "Fair Market Value"
  shall mean, with respect to any security, the per share average of the last
  reported sale prices on The Nasdaq National Market (or such other national
  stock exchange or national market system as shall then be the primary
  trading market for such security) for the ten (10) trading days immediately
  preceding the applicable date.
 
  (c) Redelivery of Shares of Ascend Common Stock. In Cascade's discretion or
if specified by Ascend in the Repurchase Notice, all or a portion of the Share
Repurchase Price shall be paid by Cascade in shares of Ascend Common Stock, by
redelivery to Ascend of the shares of Ascend Common Stock (and the
certificate(s) representing such shares) previously delivered by Ascend to
Cascade pursuant to a Stock Exercise. For purposes of this Section 7(c), each
share of Ascend Common Stock redelivered to Ascend shall be valued at and
exchanged for 1.428 shares of Cascade Common Stock. If fewer than all of the
shares of Cascade Common Stock purchased by Ascend pursuant to a Stock
Exercise are to be repurchased by Cascade pursuant to Section 7(a)(ii), Ascend
shall issue to Cascade new certificates representing those shares of Ascend
Common Stock which are not due to be redelivered to Ascend pursuant to this
Section 7(c) to the extent that excess shares of Ascend Common Stock are
included in the certificates redelivered to Ascend by Cascade. All shares of
Ascend Common Stock redelivered to Ascend hereunder shall be free and clear of
all claims, liens, charges, encumbrances and security interests of any nature
whatsoever.
 
  (d) Payment and Redelivery of Cascade Options or Shares. In the event that
Ascend exercises its rights under Section 7(a), Cascade shall, within ten (10)
business days thereafter, pay the required amount to Ascend in immediately
available funds (or shares of Ascend Common Stock, if applicable) and Ascend
shall surrender to Cascade the Cascade Option or the certificate or
certificates evidencing the shares of Cascade Common Stock purchased by Ascend
pursuant hereto, and Ascend shall warrant that it has sole beneficial
ownership of the Cascade Option or such shares and that the Cascade Option or
such shares are then free and clear of all claims, liens, charges,
encumbrances and security interests of any nature whatsoever.
 
  (e) Repurchase Price Reduced at Ascend's Option. In the event that payment
of the repurchase price specified in Section 7(a) would subject the repurchase
of the Cascade Option or the shares of Cascade Common Stock purchased by
Ascend pursuant to the Cascade Option to a vote of the stockholders of Cascade
pursuant to applicable law, regulations, or requirements of a national
securities exchange or national market system or the Cascade Charter, then
Ascend may, at its election, reduce the repurchase price or the number of
shares covered by the Ascend repurchase request to an amount which would
permit such repurchase without the necessity for such a vote.
 
  Section 8. Restrictions on Transfer.
 
  (a) Restrictions on Transfer. Prior to the fifth anniversary of the date
hereof (the "Expiration Date"), neither party shall, directly or indirectly,
by operation of law or otherwise, sell, assign, pledge, or otherwise dispose
of or transfer any shares of capital stock of the other party acquired by such
party pursuant to this Agreement, including any shares of Ascend Common Stock
issued pursuant to a Stock Exercise ("Restricted
 
                                      B-6
<PAGE>
 
Shares"), or otherwise beneficially owned (within the meaning of Rule 13d-3
promulgated under the Exchange Act) by such other party, other than (i)
pursuant to Section 7 or (ii) in accordance with Sections 8(b) or 9.
 
  (b) Permitted Sales. Following the termination of the Merger Agreement, a
party shall be permitted to sell any Restricted Shares beneficially owned by
it if such sale is made (i) pursuant to a tender or exchange offer or other
business combination transaction that has been approved or recommended, or
otherwise determined to be fair to and in the best interests of the holders of
common stock of the other party, by a majority of the members of the Board of
Directors of such other party, or (ii) subject to Section 8(c) or (d) as the
case may be, to a person who, immediately following such sale, would
beneficially own (within the meaning of Rule 13d-3 promulgated under the
Exchange Act), either alone or as part of a "group" (as used in Rule 13d-5
under the Exchange Act), not more than ten percent (10%) of such party's
outstanding voting securities, which person is a passive institutional
investor who would be eligible under Rule 13d-1(b)(1) under the Exchange Act
to report such holdings of Restricted Shares on Schedule 13G under the
Exchange Act.
 
  (c) Cascade's Right of First Refusal. At any time after the first occurrence
of a Trigger Event and prior to the Expiration Date if Ascend shall desire to
sell, assign, transfer or otherwise dispose of all or any of the shares of
Cascade Common Stock or other securities acquired by it pursuant to the
Cascade Option, it shall give Cascade written notice of the proposed
transaction (an "Ascend Offer Notice"), identifying the proposed transferee,
accompanied by a copy of a binding offer to purchase such shares or other
securities signed by such transferee and setting forth the terms of the
proposed transaction. An Ascend Offer Notice shall be deemed an offer by
Ascend to Cascade, which may be accepted within five (5) business days of the
receipt of such Ascend Offer Notice, on the same terms and conditions and at
the same price at which Ascend is proposing to transfer such shares or other
securities to such transferee. The purchase of any such shares or other
securities by Cascade shall be settled within five (5) business days of the
date of the acceptance of the offer and the purchase price shall be paid to
Ascend in immediately available funds. In the event of the failure or refusal
of Cascade to purchase all the shares or other securities covered by a Ascend
Offer Notice, Ascend may sell all, but not less than all, of such shares or
other securities to the proposed transferee at no less than the price
specified and on terms no more favorable to the transferee than those set
forth in the Ascend Offer Notice as long as such sale is completed within
ninety (90) days of the receipt by Cascade of the applicable Ascend Offer
Notice; provided that the provisions of this sentence shall not limit the
rights Ascend may otherwise have in the event Cascade has accepted the offer
contained in the Ascend Offer Notice and wrongfully refuses to purchase the
shares or other securities subject thereto. The requirements of this Section
8(c) shall not apply to (i) any disposition as a result of which the proposed
transferee would own beneficially not more than three percent (3%) of the
outstanding voting power of Cascade, (ii) any disposition of Cascade Common
Stock or other securities by a person to whom Ascend has assigned its rights
under the Cascade Option with the consent of Cascade, (iii) any sale by means
of a public offering registered under the Securities Act, or (iv) any transfer
to a wholly-owned subsidiary of Ascend which agrees in writing to be bound by
the terms hereof.
 
  (d) Ascend's Right of First Refusal. At any time after the first occurrence
of a Trigger Event and prior to the Expiration Date, if Cascade shall desire
to sell, assign, transfer or otherwise dispose of all or any of the shares of
Ascend Common Stock or other securities acquired by it pursuant to a Stock
Exercise of the Cascade Option by Ascend, it shall give Ascend written notice
of the proposed transaction (a "Cascade Offer Notice"), identifying the
proposed transferee, accompanied by a copy of a binding offer to purchase such
shares or other securities signed by such transferee and setting forth the
terms of the proposed transaction. A Cascade Offer Notice shall be deemed an
offer by Cascade to Ascend, which may be accepted within five (5) business
days of the receipt of such Cascade Offer Notice, on the same terms and
conditions and at the same price at which Cascade is proposing to transfer
such shares or other securities to such transferee. The purchase of any such
shares or other securities by Ascend shall be settled within five (5) business
days of the date of the acceptance of the offer and the purchase price shall
be paid to Cascade in immediately available funds. In the event of the failure
or refusal of Ascend to purchase all the shares or other securities covered by
a Cascade Offer Notice, Cascade may sell all, but not less than all, of such
shares or other securities to the proposed transferee at no less than the
price specified and on terms no more favorable to the transferee than those
set forth in the Cascade
 
                                      B-7
<PAGE>
 
Offer Notice as long as such sale is completed within ninety (90) days of the
receipt by Ascend of the applicable Cascade Offer Notice; provided that the
provisions of this sentence shall not limit the rights Cascade may otherwise
have in the event Ascend has accepted the offer contained in the Cascade Offer
Notice and wrongfully refuses to purchase the shares or other securities
subject thereto. The requirements of this Section 8(d) shall not apply to (i)
any disposition as a result of which the proposed transferee would own
beneficially not more than three percent (3%) of the outstanding voting power
of Ascend, (ii) any sale by means of a public offering registered under the
Securities Act, or (iii) any transfer to a wholly-owned subsidiary of Cascade
which agrees in writing to be bound by the terms hereof.
 
  (e) Additional Restrictions. Prior to any permitted sales of any Restricted
Shares under of Section 8(b)(ii), the holder thereof shall give written notice
to the issuer of such Restricted Shares of its intention to effect such
transfer. Each such notice shall describe the manner of the proposed transfer
and, if requested by the issuer of such Restricted Shares, shall be
accompanied by an opinion of counsel satisfactory to such issuer (it being
agreed that each of Gray Cary Ware & Freidenrich, A Professional Corporation,
and Testa, Hurwitz & Thibeault, LLP shall be satisfactory) to the effect that
such sale may be effected without registration under the Securities Act and
any applicable state securities laws. Each certificate for Restricted Shares
transferred as above provided shall bear the legend set forth in Section 11,
except that such certificate shall not bear such legend if (i) such transfer
is in accordance with the provisions of Rule 144 (or any other rule permitting
public sale without registration under the Securities Act) or (ii) the opinion
of counsel referred to above is to the further effect that the transferee and
any subsequent transferee would be entitled to transfer such securities in a
public sale without registration under the Securities Act and any applicable
state securities laws. The restrictions provided for in this Section 8(e)
shall not apply to securities which are not required to bear the legend
prescribed by Section 11 in accordance with the provisions of this Agreement.
The foregoing restrictions on transferability shall terminate as to any
particular shares when such shares shall have been effectively registered
under the Securities Act and any applicable state securities laws and sold or
otherwise disposed of in accordance with the registration statement covering
such shares.
 
  Section 9. Registration Rights.
 
  (a) Procedure. Following the termination of the Merger Agreement, either
party hereto that owns Restricted Shares (a "Holder") may by written notice
(the "Registration Notice") to the other party (the "Registrant") request the
Registrant to register under the Securities Act all or any part of the
Restricted Shares acquired by such Holder pursuant to this Agreement (the
"Registrable Securities") in order to permit the sale or other disposition of
such shares pursuant to a bona fide firm commitment underwritten public
offering, in which the Holder and the underwriters shall effect as wide a
distribution of such Registrable Securities as is reasonably practicable and
shall use their best efforts to prevent any person (including any "group" as
used in Rule 13d-5 under the Exchange Act)) and its affiliates from purchasing
through such offering Restricted Shares representing more than three percent
(3%) of the outstanding shares of common stock of the Registrant on a fully
diluted basis (a "Permitted Offering"). Any rights to require registration
hereunder shall terminate with respect to any shares that may be sold pursuant
to Rule 144(k) under the Securities Act.
 
  (b) Manager's Certificate. The managing underwriter shall be an investment
banking firm of nationally recognized standing, and shall be selected by (i)
the Registrant within ten (10) business days after receipt of a Registration
Notice, subject to approval of the Holder (which approval shall not be
unreasonably withheld, delayed or conditioned), or (ii) if Registrant fails to
deliver notice (the "Registrant's Designation Notice") to Holder of such
selection within ten (10) business days after receipt of a Registration
Notice, then by Holder subject to the reasonable approval of Registrant (which
approval shall not be unreasonably withheld, delayed or conditioned) (the
"Manager"), and Holder shall deliver written notice (the "Holder's Designation
Notice") of such selection within ten (10) business days after expiration of
the ten (10) day period in which Registrant is entitled to give notice. The
Registrant's Designation Notice or the Holder's Designation Notice, as the
case may be, shall state that (i) the party delivering such notice and its
proposed Manager have a good faith intention to commence promptly a Permitted
Offering, and (ii) such proposed Manager in good faith believes that, based on
the then-prevailing market conditions, it will be able to sell the Registrable
Securities to the public in a Permitted
 
                                      B-8
<PAGE>
 
Offering within one hundred twenty (120) days at a per share price equal to at
least eighty percent (80%) of the then Fair Market Value of such shares.
 
  (c) First Refusal Right. The Registrant (and/or any person designated by the
Registrant) shall thereupon have the option exercisable by written notice
delivered to the Holder within five (5) business days after the receipt of the
Registration Notice, irrevocably to agree to purchase all or any part of the
Registrable Securities proposed to be so sold for cash at a price equal to the
product of (i) the number of Registrable Securities to be so purchased by the
Registrant and (ii) the then Fair Market Value of such shares.
 
  (d) Closing. Any purchase of Registrable Securities by the Registrant (or
its designee) under Section 9(c) shall take place at a closing to be held at
the principal executive offices of the Registrant or at the offices of its
counsel at any reasonable date and time designated by the Registrant and/or
such designee in such notice within twenty (20) business days after delivery
of such notice, and any payment for the shares to be so purchased shall be
made by delivery at the time of such closing in immediately available funds.
 
  (e) Certain Limitations. If the Registrant does not elect to exercise its
option pursuant to Section 9(c) with respect to all Registrable Securities, it
shall use its best efforts to effect, as promptly as practicable, the
registration under the Securities Act of the unpurchased Registrable
Securities proposed to be so sold; provided, however, that (i) neither party
shall be entitled to demand more than an aggregate of two (2) effective
registration statements hereunder, and (ii) the Registrant will not be
required to file any such registration statement during any period of time
(not to exceed sixty (60) days after such request in the case of clause (A)
below or ninety (90) days after such request in the case of clauses (B) and
(C) below) when (A) the Registrant is in possession of material non-public
information which it reasonably believes would be detrimental to be disclosed
at such time and, in the opinion of counsel to the Registrant, such
information would be required to be disclosed if a registration statement were
filed at that time; (B) the Registrant is required under the Securities Act to
include audited financial statements for any period in such registration
statement and such financial statements are not yet available for inclusion in
such registration statement; or (C) the Registrant determines, in its
reasonable judgment, that such registration would interfere with any
financing, acquisition or other transaction involving the Registrant or any of
its material subsidiaries and that such transaction is material to the
Registrant and its subsidiaries taken as a whole. If consummation of the sale
of any Registrable Securities pursuant to a registration hereunder does not
occur within one hundred twenty (120) days after the effectiveness of the
initial registration statement, the provisions of this Section 9 shall again
be applicable to any proposed registration.
 
  (f) State Securities Laws. The Registrant shall use its reasonable best
efforts to cause any Registrable Securities registered pursuant to this
Section 9 to be qualified for sale under the securities laws of such states as
the Holder may reasonably request and shall continue such registration or
qualification in effect in such jurisdiction; provided, however, that the
Registrant shall not be required to qualify to do business in, or consent to
general service of process in, any jurisdiction by reason of this provision.
 
  (g) Obligations of Registrant. The Registrant shall provide to the
underwriters such documentation (including certificates, opinions of counsel
and "comfort" letters from auditors) as is customary in connection with
underwritten public offerings as such underwriters may reasonably require. The
registration rights set forth in this Section 9 are subject to the condition
that the Holder shall provide the Registrant with such information with
respect to its Registrable Securities, the plans for the distribution thereof,
and such other information with respect to the Holder as, in the reasonable
judgment of counsel for the Registrant, is necessary to enable the Registrant
to include in such registration statement all material facts required to be
disclosed with respect to a registration thereunder.
 
  (h) Indemnification. In connection with any registration effected under this
Section 9, the parties agree (i) to indemnify each other and the underwriters
in the customary manner, (ii) to enter into an underwriting agreement in form
and substance customary for transactions of such type with the Manager and the
other underwriters participating in such offering, and (iii) to take all
further actions which shall be reasonably
 
                                      B-9
<PAGE>
 
necessary to effect such registration and sale (including, if the Manager
deems it necessary, participating in road-show presentations).
 
  (i) Inclusion of Additional Shares of Registrant. The Registrant shall be
entitled to include (at its expense) additional shares of its common stock in
a registration effected pursuant to this Section 9 only if and to the extent
the Manager determines that such inclusion will not adversely affect the
prospects for success of such offering.
 
  Section 10. Adjustment Upon Changes in Capitalization.
 
  (a) Without limiting any restriction on Cascade contained in this Agreement
or in the Merger Agreement, in the event of any change in Cascade Common Stock
by reason of any stock dividend, stock split, merger (other than the Merger),
recapitalization, combination, exchange of shares or any similar transaction,
the type and number of shares or securities subject to the Cascade Option, and
the Exercise Price per share provided herein, shall be adjusted appropriately
and proper provision shall be made in the agreements governing such
transaction so that Ascend shall receive, upon exercise of the Cascade Option,
the number and class of securities or property that Ascend would have received
in respect of the shares of Cascade Common Stock issuable to Ascend if the
Cascade Option had been exercised immediately prior to such event or the
record date therefor, as applicable. In addition, without limiting any
restriction on Ascend or Cascade contained in this Agreement or the Merger
Agreement, in the event of any change in Ascend Common Stock or Cascade Common
Stock by reason of any stock dividend, stock split, merger (other than the
Merger), recapitalization, combination, exchange of shares or similar
transaction, equitable adjustment shall be made to the other provisions hereof
to carry out the original intent of this Agreement.
 
  (b) In the event that Cascade shall enter into an agreement: (i) to
consolidate with or merge into any person, other than Ascend or one of its
subsidiaries, and shall not be the continuing or surviving corporation of such
consolidation or merger; (ii) to permit any person, other than Ascend or one
of its Subsidiaries, to merge into Cascade and Cascade shall be the continuing
or surviving corporation, but, in connection with such merger, the then-
outstanding shares of Cascade Common Stock shall be changed into or exchanged
for stock or other securities of Cascade or any other person or cash or any
other property; or (iii) to sell or otherwise transfer all or substantially
all of its assets to any person, other than Ascend or one of its Subsidiaries,
then, and in each such case, the agreement governing such transaction shall
make proper provision so that upon the consummation of such transaction and
upon the subsequent exercise of the Cascade Option, Ascend shall be entitled
to receive, for each share of Cascade Common Stock with respect to which the
Cascade Option has not theretofore been exercised, an amount of consideration
in the form of and equal to the per share amount of consideration that would
be received by the holder of one share of Cascade Common Stock (and, in the
event of an election or similar arrangement with respect to the type of
consideration to be received by the holders of Cascade Common Stock, subject
to the foregoing, proper provision shall be made so that the holder of the
Cascade Option would have the same election or similar rights as would the
holder of the number of shares of Cascade Common Stock for which the Cascade
Option is then exercisable).
 
  Section 11. Restrictive Legends. Each certificate representing shares of
Cascade Common Stock issued to Ascend hereunder, and shares of Ascend Common
Stock, if any, delivered to Cascade pursuant to a Stock Exercise, shall
include a legend in substantially the following form:
 
  THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
  UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR ANY STATE SECURITIES OR
  BLUE SKY LAWS, AND MAY BE REOFFERED OR SOLD ONLY IF SO REGISTERED OR IF AN
  EXEMPTION FROM SUCH REGISTRATION IS AVAILABLE. SUCH SECURITIES ARE ALSO
  SUBJECT TO ADDITIONAL RESTRICTIONS ON TRANSFER AS SET FORTH IN THE CASCADE
  STOCK OPTION AGREEMENT DATED AS OF MARCH 30, 1997, A COPY OF WHICH MAY BE
  OBTAINED FROM THE ISSUER UPON REQUEST.
 
It is understood and agreed that (i) the reference to the resale restrictions
of the Securities Act and state securities or Blue Sky laws in the foregoing
legend shall be removed by delivery of substitute certificate(s) without such
 
                                     B-10
<PAGE>
 
reference if Ascend or Cascade, as the case may be, shall have delivered to
the other party a copy of a letter from the staff of the Securities and
Exchange Commission, or an opinion of counsel, in form and substance
reasonably satisfactory to the other party, to the effect that such legend is
not required for purposes of the Securities Act or such laws; (ii) the
reference to the provisions of this Agreement in the foregoing legend shall be
removed by delivery of substitute certificate(s) without such reference if the
shares have been sold or transferred in compliance with the provisions of this
Agreement and under circumstances that do not require the retention of such
reference; and (iii) the legend shall be removed in its entirety if the
conditions in the preceding clauses (i) and (ii) are both satisfied. In
addition, such certificates shall bear any other legend as may be required by
law. Certificates representing shares sold in a registered public offering
pursuant to Section 9 shall not be required to bear the legend set forth in
this Section 11.
 
  Section 12. Binding Effect; No Assignment; No Third-Party
Beneficiaries. This Agreement shall be binding upon and inure to the benefit
of the parties hereto and their respective successors and permitted assigns.
Except as expressly provided for in this Agreement, neither this Agreement nor
the rights or obligations of either party hereto are assignable, except by
operation of law, or with the written consent of the other party, and any such
attempted assignment in violation of this Agreement shall be void and of no
force or effect. Nothing contained in this Agreement, express or implied, is
intended to confer upon any person other than the parties hereto and their
respective permitted assigns any rights or remedies of any nature whatsoever.
Any Restricted Shares sold by a party in compliance with the provisions of
Section 9 shall, upon consummation of such sale, be free of the restrictions
imposed and the benefits provided with respect to such shares by this
Agreement.
 
  Section 13. Specific Performance. The parties hereto recognize and agree
that if for any reason any of the provisions of this Agreement are not
performed in accordance with their specific terms or are otherwise breached,
immediate and irreparable harm or injury would be caused for which money
damages would not be an adequate remedy. Accordingly, each party agrees that,
in addition to other remedies, whether at law or in equity, the other party
shall be entitled to an injunction to prevent or restrain any violation or
threatened violation of the provisions of this Agreement, and to enforce
specifically the terms and provisions hereof, in any court of the State of
Delaware or of the United States of America located in the State of Delaware.
In the event that any action should be brought in equity to enforce the
provisions of this Agreement, neither party will allege, and each party hereby
waives the defense, that there is an adequate remedy at law. Each party hereto
irrevocably and unconditionally consents and submits to the jurisdiction of
the courts of the State of Delaware and of the United States of America
located in the City of Wilmington in the State of Delaware for any actions,
suits or proceedings arising out of or relating to this Agreement and the
transactions contemplated hereby, and waives any objection to venue in any
such court therein.
 
  Section 14. Validity.
 
  (a) The invalidity or unenforceability of any provision of this Agreement
shall not affect the validity or enforceability of the other provisions of
this Agreement, which shall remain in full force and effect.
 
  (b) In the event any court or other governmental or regulatory authority
holds any provisions of this Agreement to be null, void or unenforceable, the
parties hereto shall negotiate in good faith the execution and delivery of an
amendment to this Agreement in order, as nearly as possible, to effectuate, to
the extent permitted by law, the intent of the parties hereto with respect to
such provision and the economic effects thereof.
 
  (c) If for any reason any such court or other governmental or regulatory
authority determines that Ascend is not permitted to acquire, or Cascade is
not permitted to repurchase pursuant to Section 7, the full number of shares
of Cascade Common Stock provided in this Agreement (as the same may be
adjusted), it is the express intention of Cascade to allow Ascend to acquire
or to require Cascade to repurchase such lesser number of shares as may be
permissible without any other amendment or modification hereof.
 
  (d) Each party agrees that, should any court or other governmental or
regulatory authority hold any provision of this Agreement or part hereof to be
null, void or unenforceable, or order any party to take any action
 
                                     B-11
<PAGE>
 
inconsistent herewith, or not take any action required herein, the other party
shall not be entitled to specific performance of such provision or part hereof
or to any other remedy, including but not limited to money damages, for breach
hereof or of any other provision of this Agreement or part hereof as the
result of such holding or order.
 
  Section 15. Notices. All notices and other communications hereunder shall be
in writing and shall be deemed given if (a) delivered personally, or (b) if
sent by overnight courier service (receipt confirmed in writing), or (c) if
delivered by facsimile transmission (with receipt confirmed), or (d) five (5)
days after being mailed by registered or certified mail (return receipt
requested) to the parties in each case to the following addresses (or at such
other address for a party as shall be specified by like notice):
 
    If to Cascade, to:
 
    Cascade Communications Corp.
    5 Carlisle Road
    Westford, MA 01886
    Facsimile No.: (508) 692-1221
    Attention: President and Corporate Counsel
 
    with a copy to:
 
    Testa, Hurwitz & Thibeault, LLP
    High Street Tower
    125 High Street
    Boston, MA 02110
    Fax Number: (617) 248-7100
    Attention: John A. Meltaus, Esq.
 
    If to Ascend, to:
 
    Ascend Communications, Inc.
    One Ascend Plaza
    1701 Harbor Bay Parkway
    Alameda, CA 94502
    Facsimile No.: (510) 769-6001
    Attention: President
 
    with a copy to:
 
    Gray Cary Ware & Freidenrich
    A Professional Corporation
    400 Hamilton Avenue
    Palo Alto, CA 94301
    Fax Number: (415) 327-3699
    Attention: Gregory M. Gallo, Esq. &
               Rod J. Howard, Esq.
 
  Section 16. Governing Law. This Agreement shall be governed by and
construed, and any controversy arising out of or otherwise relating to this
Agreement shall be determined, in accordance with the laws of the State of
Delaware applicable to agreements made and to be performed entirely within
such State and without regard to its choice of law principles. Each party
hereto consents and submits to the exclusive jurisdiction of the courts of the
State of Delaware and the courts of the United States located in such state
for the adjudication of any action, suit, proceeding, claim or dispute arising
out of or otherwise relating to this Agreement.
 
  Section 17. Interpretation. The headings contained in this Agreement are for
reference purposes and shall not affect in any way the meaning or
interpretation of the Agreement. When reference is made in this Agreement to a
Section, such reference shall be to a Section of this Agreement, unless
otherwise indicated. Whenever the words "include," "includes," or "including"
are used in this Agreement, they shall be deemed
 
                                     B-12
<PAGE>
 
to be followed by the words "without limitation." Whenever "or" is used in
this Agreement it shall be construed in the nonexclusive sense. The words
"herein," "hereby," "hereof," "hereto," "hereunder" and words of similar
import refer to this Agreement.
 
  Section 18. Counterparts; Effect. This Agreement may be executed in two or
more counterparts, each of which shall be deemed to be an original, but all of
which shall constitute one and the same agreement.
 
  Section 19. Expenses. Cascade shall pay all expenses, and any and all
federal, state and local taxes and other charges, that may be payable in
connection with the preparation, issuance and delivery of Cascade stock
certificates under Section 4 and any stock listing or stock quotation
application required to be filed by Cascade with respect to such shares, and
Ascend shall pay all expenses, and any and all federal, state and local taxes
and other charges, that may be payable in connection with the preparation,
issuance and delivery of Ascend stock certificates in connection with a Stock
Exercise and any stock listing or stock quotation application required to be
filed by Cascade with respect to such shares. A registration effected under
Section 9 shall be effected at the Registrant's expense, except for
underwriting discounts and commissions and the fees and the expenses of
counsel to the Holder. Subject to the foregoing, and except as otherwise
expressly provided herein or in the Merger Agreement, all other costs and
expenses incurred in connection with the transactions contemplated by this
Agreement shall be paid by the party incurring such expenses.
 
  Section 20. Amendments; Waiver. This Agreement may be amended by the parties
hereto and the terms and conditions hereof may be waived only by an instrument
in writing signed on behalf of each of the parties hereto, or, in the case of
a waiver, by an instrument signed on behalf of the party waiving compliance.
 
  Section 21. Extension of Time Periods. The time periods for exercises of
certain rights hereunder shall be extended (but in no event by more than six
(6) months): (a) to the extent necessary to obtain all governmental approvals
for the exercise of such rights, and for the expiration of all statutory
waiting periods; and (b) to the extent necessary to avoid any liability or
disgorgement of profits under Section 16(b) of the Exchange Act by reason of
such exercise.
 
  Section 22. Further Assurances. Each party agrees to execute and deliver all
such further documents and instruments and take all such further action as may
be necessary in order to consummate the transactions contemplated hereby.
 
                 [Remainder of Page Intentionally Left Blank]
 
 
                                     B-13
<PAGE>
 
  IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed by their respective duly authorized officers as of the date first
above written.
 
                                          Cascade Communications Corp.
 
                                          By: /s/ DANIEL E. SMITH
                                              _________________________________
                                            Name: Daniel E. Smith
                                            Title: President and Chief 
                                                   Executive Officer
 
                                          Ascend Communications, Inc.
 
                                          By: /s/ ROBERT K. DAHL
                                              _________________________________
                                            Name: Robert K. Dahl
                                            Title: Vice President, Finance,
                                                   and Chief Financial Officer
 
                                      B-14

<PAGE>
 
                                                                      EXHIBIT 2
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
                         ASCEND STOCK OPTION AGREEMENT
 
                                 BY AND BETWEEN
 
                          ASCEND COMMUNICATIONS, INC.,
                            A DELAWARE CORPORATION,
 
                                      AND
 
                         CASCADE COMMUNICATIONS CORP.,
                            A DELAWARE CORPORATION,
 
 
 
                           DATED AS OF MARCH 30, 1997
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
 
                             TABLE OF DEFINED TERMS
 
<TABLE>
<CAPTION>
TERM                                                                   SECTION
- ----                                                                   --------
<S>                                                                    <C>
Agreement............................................................. Preamble
Ascend................................................................ Preamble
Ascend Common Stock................................................... Recitals
Ascend Offer Notice................................................... 8(d)
Ascend Option......................................................... 1
Cash Exercise......................................................... 2(e)
Cash Exercise Price................................................... 2(e)
Cascade............................................................... Preamble
Cascade Charter....................................................... 2(b)
Cascade Common Stock.................................................. 2(e)
Cascade Offer Notice.................................................. 8(c)
Closing............................................................... 2(b)
Exercise Notice....................................................... 2(b)
Exercise Price........................................................ 2(e)
Expiration Date....................................................... 8(a)
Fair Market Value..................................................... 7(b)(iii)
Holder................................................................ 9(a)
Holder's Designation Notice........................................... 9(b)
HSR Act............................................................... 3
Manager............................................................... 9(b)
Material Contract..................................................... 5(e)
Merger................................................................ Recitals
Merger Agreement...................................................... Recitals
Net Proceeds.......................................................... 2(f)
Option Number......................................................... 2(d)
Option Repurchase Price............................................... 7(b)(i)
Permitted Offering.................................................... 9(a)
Purchase Period....................................................... 7(a)
Registrable Securities................................................ 9(a)
Registrant............................................................ 9(a)
Registrant's Designation Notice....................................... 9(b)
Registration Notice................................................... 9(a)
Repurchase Notice..................................................... 7(a)
Restricted Shares..................................................... 8(a)
Share Repurchase Price................................................ 7(b)(ii)
Stock Exercise........................................................ 2(e)
Stock Exercise Price.................................................. 2(e)
Sub................................................................... Recitals
Trigger Event......................................................... 2(a)
Violation............................................................. 5(e)
</TABLE>
 
                                       i
<PAGE>
 
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                                            PAGE
                                                                            ----
 <C>     <C>  <S>                                                           <C>
 Section 1.   Grant of Option.............................................  B-1
 Section 2.   Exercise and Termination of the Ascend Option...............  B-1
         (a)  Exercise....................................................  B-1
         (b)  Exercise Procedure..........................................  B-1
         (c)  Termination of the Ascend Option............................  B-2
         (d)  Option Number...............................................  B-2
         (e)  Exercise Price..............................................  B-2
         (f)  Certain Limitations.........................................  B-2
 Section 3.   Conditions to Closing.......................................  B-3
 Section 4.   Closing.....................................................  B-3
 Section 5.   Representations and Warranties of Ascend....................  B-3
         (a)  Organization and Standing...................................  B-3
         (b)  Authority...................................................  B-3
         (c)  Reservation of Shares.......................................  B-3
         (d)  No Liens....................................................  B-4
         (e)  No Conflicts................................................  B-4
         (f)  Consents and Approvals......................................  B-4
         (g)  Investment Purposes.........................................  B-4
 Section 6.   Representations and Warranties of Cascade...................  B-4
         (a)  Organization and Standing...................................  B-4
         (b)  Authority...................................................  B-4
         (c)  Reservation of Shares.......................................  B-5
         (d)  No Liens....................................................  B-5
         (e)  No Conflicts................................................  B-5
         (f)  Consents and Approvals......................................  B-5
         (g)  Investment Purpose..........................................  B-5
 Section 7.   Certain Repurchases.........................................  B-5
         (a)  Cascade "Put"...............................................  B-5
         (b)  Certain Definitions.........................................  B-5
         (c)  Redelivery of Shares of Cascade Common Stock................  B-6
         (d)  Payment and Redelivery of Ascend Options or Shares..........  B-6
         (e)  Repurchase Price Reduced at Cascade's Option................  B-6
 Section 8.   Restrictions on Transfer....................................  B-6
         (a)  Restrictions on Transfer....................................  B-6
         (b)  Permitted Sales.............................................  B-7
         (c)  Ascend's Right of First Refusal.............................  B-7
         (d)  Cascade's Right of First Refusal............................  B-7
         (e)  Additional Restrictions.....................................  B-8
 Section 9.   Registration Rights.........................................  B-8
         (a)  Procedure...................................................  B-8
         (b)  Manager's Certificate.......................................  B-8
         (c)  First Refusal Right.........................................  B-9
         (d)  Closing.....................................................  B-9
         (e)  Certain Limitations.........................................  B-9
         (f)  State Securities Laws.......................................  B-9
         (g)  Obligations of Registrant...................................  B-9
         (h)  Indemnification.............................................  B-9
         (i)  Inclusion of Additional Shares of Registrant................  B-9
</TABLE>
 
                                       ii
<PAGE>
 
<TABLE>
<CAPTION>
                                                                          PAGE
                                                                          ----
 <C>   <C>   <S>                                                          <C>
 Section 10. Adjustment Upon Changes in Capitalization..................  B-10
 Section 11. Restrictive Legends........................................  B-10
             Binding Effect; No Assignment; No Third-Party
 Section 12.  Beneficiaries.............................................  B-11
 Section 13. Specific Performance.......................................  B-11
 Section 14. Validity...................................................  B-11
 Section 15. Notices....................................................  B-12
 Section 16. Governing Law..............................................  B-12
 Section 17. Interpretation.............................................  B-12
 Section 18. Counterparts; Effect.......................................  B-13
 Section 19. Expenses...................................................  B-13
 Section 20. Amendments; Waiver.........................................  B-13
 Section 21. Extension of Time Periods..................................  B-13
 Section 22. Further Assurances.........................................  B-13
</TABLE>
 
                                      iii
<PAGE>
 
                         ASCEND STOCK OPTION AGREEMENT
 
  THIS ASCEND STOCK OPTION AGREEMENT (the "Agreement") is made and entered
into as of March 30, 1997 by and between Ascend Communications, Inc., a
Delaware corporation ("Ascend"), and Cascade Communications Corp., a Delaware
corporation ("Cascade").
 
                                   Recitals
 
  Concurrently with the execution and delivery of this Agreement, Ascend,
Cascade, and Cascade Merger Corporation, a Delaware corporation and a wholly-
owned subsidiary of Ascend ("Sub"), are entering into an Agreement and Plan of
Reorganization, dated as of March 30, 1997 (the "Merger Agreement"), which
provides for the merger of Sub with and into Cascade in accordance with the
terms of the Merger Agreement and the laws of the State of Delaware (the
"Merger"). As a condition and inducement to Cascade's willingness to enter
into the Merger Agreement, Cascade has requested that Ascend agree, and Ascend
has agreed, to grant to Cascade an option to acquire certain shares of
Ascend's authorized but unissued common stock, par value $.001 per share
(together with any associated rights, "Ascend Common Stock"), on the terms and
subject to the conditions set forth herein.
 
  NOW, THEREFORE, to induce Cascade to enter into the Merger Agreement and in
consideration of the representations, warranties, covenants and agreements
contained herein and in the Merger Agreement, the parties hereto, intending to
be legally bound, hereby agree as follows. Capitalized terms used herein but
not defined herein shall have the meanings ascribed to them in the Merger
Agreement.
 
                                   Agreement
 
  Section 1. Grant of Option. Ascend hereby grants to Cascade an irrevocable
option (the "Ascend Option") to purchase a number of shares of Ascend Common
Stock equal to the Option Number (as defined in Section 2(d)), on the terms
and subject to the conditions set forth below.
 
  Section 2. Exercise and Termination of the Ascend Option.
 
    (a) Exercise. The Ascend Option may be exercised by Cascade, in whole or
  in part, at any time or from time to time prior to the termination of
  Cascade's right to exercise the Ascend Option by the terms of this Agreement
  and upon and after the occurrence of the earliest event which causes (i) the
  Ascend Termination Fee or (ii) the Ascend Post-Termination Fee (in each case
  as defined in the Merger Agreement) to become payable (a "Trigger Event").
  Notwithstanding the foregoing, the Ascend Option may not be exercised if
  Cascade is in breach in any material respect of any of its material
  representations, warranties, covenants or agreements contained in this
  Agreement or the Merger Agreement.
 
    (b) Exercise Procedure. In the event that Cascade wishes to exercise the
  Ascend Option, Cascade shall deliver to Ascend written notice (an "Exercise
  Notice") specifying the total number of shares of Ascend Common Stock that
  Cascade wishes to purchase. To the extent permitted by law and the
  Certificate of Incorporation, as amended, of Ascend (the "Ascend Charter"),
  and provided that the conditions set forth in Section 3 to Ascend's
  obligation to issue the shares of Ascend Common Stock to Cascade hereunder
  have been satisfied or waived, Cascade shall, upon delivery of the Exercise
  Notice and tender of the applicable aggregate Exercise Price, immediately
  be deemed to be the holder of record of the shares of Ascend Common Stock
  issuable upon such exercise, notwithstanding that the stock transfer books
  of Ascend shall then be closed or that certificates representing such
  shares of Ascend Common Stock shall not theretofore have been delivered to
  Cascade. Each closing of a purchase of shares of Ascend Common Stock
  hereunder (a "Closing") shall occur at a place, on a date, and at a time
  designated by Cascade in an Exercise Notice delivered at least two (2)
  business days prior to the date of such Closing.
 
                                      C-1
<PAGE>
 
    (c) Termination of the Ascend Option. Cascade's right to exercise the
  Ascend Option shall terminate upon the earliest to occur of:
 
      (i) the Effective Time of the Merger;
 
      (ii) the date on which the Merger Agreement is terminated pursuant to
    Article VIII thereof other than under circumstances which also
    constitute a Trigger Event under this Agreement; and
 
      (iii) (A) in the event the Ascend Option becomes exercisable pursuant to
    clause (i) of Section 2(a), the date two hundred seventy (270) days after
    the date on which the Merger Agreement is terminated pursuant to Article
    VIII thereof under circumstances which also constitute a Trigger Event under
    clause (i) of Section 2(a), or
 
      (B) in the event the Ascend Option becomes exercisable pursuant to clause
    (ii) of Section 2(a), the later of (I) the date two hundred seventy (270)
    days after the date on which the Merger Agreement is terminated pursuant to
    Article VIII thereof under circumstances which also constitute a Trigger
    Event under clause (ii) of Section 2(a) and (II) the date one hundred eighty
    (180) days after the date on which the Ascend Option becomes exercisable
    pursuant to clause (ii) of Section 2(a).
 
Notwithstanding the foregoing, with respect to clause (iii) in the immediately
preceding sentence, if the Ascend Option cannot be exercised by reason of any
applicable judicial or governmental judgment, decree, order, law or
regulation, the Ascend Option shall remain exercisable and shall not terminate
until the earlier of (x) the date on which such impediment shall become final
and not subject to appeal and (y) 5:00 p.m., Pacific Standard Time, on the
tenth (10th) business day after such impediment shall have been removed;
provided, however, that if such judgment, decree, or order shall have been
obtained at the request of Ascend or any of its Affiliates or a party that has
made or is proposing to make a Competing Offer (as such term is defined in
the Merger Agreement)for Ascend, and such judgment, decree or order is vacated,
set aside, withdrawn, reversed or otherwise nullified, the time during which the
Ascend Option shall remain exercisable shall be extended for as long as such
judgment, decree, or order shall be in effect. The rights of Cascade set forth
in Sections 7 and 9 shall not terminate upon termination of Cascade's right to
exercise the Ascend Option with respect to shares acquired prior to termination,
but shall extend to the time provided in such sections. Notwithstanding the
termination of the Ascend Option, Cascade shall be entitled to purchase the
shares of Ascend Common Stock with respect to which Cascade had exercised the
Ascend Option prior to such termination.
 
    (d) Option Number. The aggregate number of shares of Ascend Common Stock
  issuable upon exercise of this Ascend Option (the "Option Number") shall
  initially be the number of shares, rounded down to the nearest whole share,
  equal to nineteen and nine-tenths percent (19.9%) of the total number of
  shares of Ascend Common Stock issued and outstanding as of the date of this
  Agreement, and shall be adjusted hereafter to reflect changes in Ascend's
  capitalization occurring after the date hereof in accordance with Section
  10. Notwithstanding any other provision of this Agreement, in no event
  shall the Option Number exceed nineteen and nine-tenths percent (19.9%) of
  the total number of shares of Ascend Common Stock issued and outstanding as
  of the date of this Agreement, adjusted in accordance with Section 10.
 
    (e) Exercise Price. The purchase price per share of Ascend Common Stock
  pursuant to the Ascend Option (the "Exercise Price") shall be payable, at
  Cascade's election, in cash (a "Cash Exercise") or in shares (a "Stock
  Exercise") of Cascade common stock, $.001 par value per share ("Cascade Common
  Stock"). The Exercise Price per share of Ascend Common Stock, (i) in the case
  of a Cash Exercise, shall be a cash amount equal to $52.00 (the "Cash Exercise
  Price"), and (ii) in the case of a Stock Exercise, shall be 1.833 shares of
  Cascade Common Stock (the "Stock Exercise Price").
 
    (f) Certain Limitations. In the event Cascade would receive aggregate,
  cumulative Net Proceeds (as defined below) of more than eighty-five million
  dollars ($85,000,000) in connection with the sale (or other disposition) to
  any third party of the shares of Ascend Common Stock acquired pursuant to
  the Ascend Option (other than a sale of such shares to Ascend pursuant to
  Section 7, all Net Proceeds in excess of such amount shall be remitted to
  Ascend promptly upon receipt. "Net Proceeds" shall mean the aggregate
  proceeds of such sale or disposition in excess of the product of the
  Exercise Price multiplied by the number of shares of Ascend Common Stock
  included in such sale or disposition. Notwithstanding anything in this
 
                                      C-2
<PAGE>
 
  Agreement or in the Merger Agreement to the contrary, the maximum aggregate
  amount payable by Ascend to Cascade and its affiliates pursuant to Section
  7 of this Agreement and the provisions of Section 8.3(c) of the Merger
  Agreement shall not exceed the sum of eighty-five million dollars
  ($85,000,000) plus, in the case of payments pursuant to Sections 7(a)(ii)
  and 7(b)(ii) of this Agreement, the aggregate Exercise Price for the shares
  of Ascend Common Stock repurchased by Ascend from Cascade pursuant to
  Section 7 of this Agreement, it being understood that the limitation
  contained in this sentence shall not limit the amounts receivable by
  Cascade from persons other than Ascend, including without limitation
  amounts receivable pursuant to a tender offer or other purchase and sale
  transaction.
 
  Section 3. Conditions to Closing. The obligation of Ascend to issue the
shares of Ascend Common Stock to Cascade hereunder is subject to the
conditions that (a) all waiting periods, if any, under the Hart Scott Rodino
Antitrust Improvements Act of 1975, as amended (the "HSR Act"), applicable to
the issuance of the shares of Ascend Common Stock by Ascend and the
acquisition of such shares by Cascade hereunder (and, in the case of a Stock
Exercise, the issuance of shares of Cascade Common Stock by Cascade and the
acquisition of such shares by Ascend) shall have expired or have been
terminated; (b) no preliminary or permanent injunction or other order by any
court of competent jurisdiction prohibiting or otherwise restraining such
issuance shall be in effect; and (c) all consents, approvals, orders,
authorizations and permits of any federal, state, local or foreign
governmental authority, if any, required in connection with the issuance of
the shares of Ascend Common Stock and the acquisition of such shares by
Cascade hereunder (and, in the case of a Stock Exercise, the issuance of
shares of Cascade Common Stock and the acquisition of such shares by Ascend)
shall have been obtained.
 
  Section 4. Closing. At any Closing: (a) Ascend shall deliver to Cascade or
its designee a single certificate in definitive form representing the number
of shares of Ascend Common Stock designated by Cascade in its Exercise Notice,
such certificate to be registered in the name of Cascade and to bear the
legend set forth in Section 11; and (b) Cascade shall deliver to Ascend the
aggregate Exercise Price for the shares of Ascend Common Stock so designated
and being purchased by (i) wire transfer of immediately available funds to the
account or accounts specified in writing by Ascend (in the case of a Cash
Exercise), or (ii) subject to the satisfaction of applicable conditions,
delivery of a certificate or certificates representing the number of shares of
Cascade Common Stock being issued by Cascade in consideration thereof (in the
case of a Stock Exercise). Effective at or prior to the Closing, Ascend shall
cause the shares of Ascend Common Stock being delivered at the Closing to be
approved for quotation on The Nasdaq National Market, and Cascade shall cause
the shares of Cascade Common Stock being delivered at the Closing pursuant to
a Stock Exercise to be approved for quotation on The Nasdaq National Market.
 
  Section 5. Representations and Warranties of Ascend. Ascend represents and
warrants to Cascade as follows:
 
    (a) Organization and Standing. Ascend is a corporation duly organized,
  validly existing and in good standing under the laws of the State of
  Delaware and has all corporate power and authority required to enter into
  this Agreement and to carry out its obligations hereunder.
 
    (b) Authority. The execution and delivery of this Agreement by Ascend and
  the consummation by Ascend of the transactions contemplated hereby have
  been duly authorized by all necessary corporate action on the part of
  Ascend and no other corporate proceedings on the part of Ascend and no
  action of Ascend shareholders are necessary to authorize this Agreement or
  any of the transactions contemplated hereby; this Agreement has been duly
  and validly executed and delivered by Ascend and, assuming the due
  authorization, execution and delivery hereof by Cascade and the receipt of
  all required governmental approvals, constitutes the valid and binding
  obligation of Ascend, enforceable against Ascend in accordance with its
  terms, except as may be limited by applicable bankruptcy, insolvency,
  reorganization or other similar laws affecting the enforcement of
  creditors' rights generally, and except that the availability of equitable
  remedies, including specific performance, may be subject to the discretion
  of any court before which any proceeding therefor may be brought.
 
    (c) Reservation of Shares. Ascend has taken all necessary corporate
  action to authorize and reserve for issuance and to permit it to issue,
  upon exercise of the Ascend Option, and at all times from the date
 
                                      C-3
<PAGE>
 
  hereof through the expiration of the Ascend Option will have reserved, a
  number of authorized and unissued shares of Ascend Common Stock not less
  than the Option Number, such amount being subject to adjustment as provided
  in Section 10, all of which, upon their issuance and delivery in accordance
  with the terms of this Agreement, will be duly authorized, validly issued,
  fully paid and nonassessable.
 
    (d) No Liens. The shares of Ascend Common Stock issued to Cascade upon
  the exercise of the Ascend Option will be, upon delivery thereof to
  Cascade, free and clear of all claims, liens, charges, encumbrances and
  security interests of any nature whatsoever.
 
    (e) No Conflicts. The execution and delivery of this Agreement by Ascend
  does not, and, subject to compliance with applicable law, the consummation
  by Ascend of the transactions contemplated hereby will not, violate,
  conflict with, or result in a breach of any provision of, or constitute a
  default (with or without notice or lapse of time, or both) under, or result
  in the termination of, or accelerate the performance required by, or result
  in a right of termination, cancellation, or acceleration of any obligation
  or the loss of a material benefit under, or the creation of a lien, pledge,
  security interest or other encumbrance on assets (any such violation,
  conflict, breach, default, termination, acceleration, right of termination,
  cancellation or acceleration, loss, or creation, a "Violation") by Ascend
  or any of its Subsidiaries of (i) any provision of the charter or the
  Bylaws of Ascend or any of its Subsidiaries, each as amended to date, (ii)
  any material provision of any material loan or credit agreement, note,
  mortgage, indenture, lease, benefit plan or other agreement, obligation,
  instrument, permit, concession, franchise or license (a "Material
  Contract") of Ascend or any of its Subsidiaries or to which any of them is
  a party or by which any of them or their properties or assets are bound, or
  (iii) except as contemplated by Section 4.4(c) of the Merger Agreement or
  Section 5(f) below, any judgment, order, decree, statute, law, ordinance,
  rule or regulation applicable to Ascend or any of its subsidiaries or any
  of their properties or assets.
 
    (f) Consents and Approvals. The execution and delivery of this Agreement
  by Ascend does not, and (except for the notifications required under the
  HSR Act and applicable foreign laws, the expiration or early termination of
  any waiting periods under the HSR Act and applicable foreign laws, and the
  receipt of approvals under applicable securities laws, and except as
  contemplated by Section 9), the performance of this Agreement by Ascend and
  the consummation of the transactions contemplated hereby will not, require
  any consent, approval, order, authorization or permit of, filing with, or
  notification to any governmental or regulatory authority, other than such
  consents, approvals, orders, authorizations, permits, filings and
  notifications which, in the aggregate, if not obtained or made, could not
  reasonably be expected to have a Cascade Material Adverse Effect or an
  Ascend Material Adverse Effect (as such terms are defined in the Merger
  Agreement) or a material adverse effect on the ability of the parties to
  consummate the transactions contemplated by this Agreement.
 
    (g) Investment Purposes. Any shares of Cascade Common Stock acquired by
  Ascend pursuant to this Agreement will be acquired for Ascend's own
  account, for investment purposes only, and will not be acquired by Ascend
  with a view to the public distribution thereof in violation of any
  applicable provision of the Securities Act.
 
  Section 6. Representations and Warranties of Cascade. Cascade represents and
warrants to Ascend as follows:
 
    (a) Organization and Standing. Cascade is a corporation duly organized,
  validly existing and in good standing under the laws of the State of
  Delaware and has all corporate power and authority required to enter into
  this Agreement and to carry out its obligations hereunder.
 
    (b) Authority. Except as set forth in Section 6(c), the execution and
  delivery of this Agreement by Cascade and the consummation by Cascade of
  the transactions contemplated hereby have been duly authorized by all
  necessary corporate action on the part of Cascade, and no other corporate
  proceedings on the part of Cascade and no action of its stockholders are
  necessary to authorize this Agreement or any of the transactions
  contemplated hereby; this Agreement has been duly and validly executed and
  delivered by Cascade and, assuming the due authorization, execution and
  delivery hereof by Ascend and the receipt of all required governmental
  approvals, constitutes the valid and binding obligation of Cascade,
  enforceable
 
                                      C-4
<PAGE>
 
  against Cascade in accordance with its terms, except as may be limited by
  applicable bankruptcy, insolvency, reorganization, or other similar laws
  affecting the enforcement of creditors' rights generally, and except that
  the availability of equitable remedies, including specific performance, may
  be subject to the discretion of any court before which any proceeding may
  be brought.
 
    (c) Reservation of Shares. Prior to any delivery of shares of Cascade
  Common Stock in consideration of the purchase of shares of Ascend Common
  Stock pursuant hereto, Cascade will have taken all necessary corporate
  action to authorize for issuance and to permit it to issue such shares of
  Cascade Common Stock, all of which, upon their issuance and delivery in
  accordance with the terms of this Agreement, will be duly authorized,
  validly issued, fully paid and nonassessable.
 
    (d) No Liens. The shares of Cascade Common Stock (if any) issued to
  Ascend in consideration of the purchase of shares of Ascend Common Stock
  pursuant hereto will be, upon delivery thereof to Ascend, free and clear of
  all claims, liens, charges, encumbrances and security interests of any
  nature whatsoever.
 
    (e) No Conflicts. The execution and delivery of this Agreement by Cascade
  does not, and the consummation by Cascade of the transactions contemplated
  hereby will not, violate, conflict with, or result in a Violation by
  Cascade or any of its Subsidiaries of (i) any provision of the Certificate
  of Incorporation or Bylaws of Cascade, (ii) any material provision of any
  Material Contract of Cascade or any of its Subsidiaries or to which any of
  them is a party or by which any of them or their properties or assets are
  bound, or (iii) except as contemplated by Section 3.4(c) of the Merger
  Agreement or Section 6(f) below, any judgment, order, decree, statute, law,
  ordinance, rule or regulation applicable to Cascade or any of its
  subsidiaries or any of their properties or assets.
 
    (f) Consents and Approvals. The execution and delivery of this Agreement
  by Cascade does not, and (except for the notifications required under the
  HSR Act and applicable foreign laws, the expiration or early termination of
  waiting periods under the HSR Act and applicable foreign laws, and the
  receipt of approvals under applicable securities laws, and except as
  contemplated by Section 9), the performance of this Agreement by Ascend and
  the consummation of the transactions contemplated hereby will not, require
  any consent, approval, order, authorization or permit of, filing with, or
  notification to any governmental or regulatory authority, other than such
  consents, approvals, orders, authorizations, permits, filings and
  notifications which, in the aggregate, if not obtained or made, could not
  reasonably be expected to have a Cascade Material Adverse Effect or an
  Ascend Material Adverse Effect (as such terms are defined in the Merger
  Agreement) or a material adverse effect on the ability of the parties to
  consummate the transactions contemplated by this Agreement.
 
    (g) Investment Purpose. Any shares of Ascend Common Stock acquired by
  Cascade upon exercise of the Ascend Option will be acquired for Cascade's
  own account, for investment purposes only and will not be, and the Ascend
  Option is not being, acquired by Cascade with a view to the public
  distribution thereof in violation of any applicable provision of the
  Securities Act.
 
  Section 7. Certain Repurchases.
 
    (a) Cascade "Put". At any time during which the Ascend Option is
  exercisable pursuant to Section 2 (the "Purchase Period") upon written
  notice to Ascend by Cascade (the "Repurchase Notice"):
 
      (i) Ascend and its successors in interest shall repurchase from
    Cascade all or any portion of the Ascend Option, as specified by
    Cascade, to the extent not previously exercised, at the Option
    Repurchase Price set forth in Section 7(b)(i), subject to and as
    limited by Section 2(f) above; and
 
      (ii) Ascend and its successors in interest shall repurchase from
    Cascade all or any portion of the shares of Ascend Common Stock
    purchased by Cascade pursuant to the Ascend Option, as specified by
    Cascade, at the Share Repurchase Price set forth in Section 7(b)(ii)
    subject to and as limited by Section 2(f) above.
 
    (b) Certain Definitions. For purposes of this Section 7, the following
  definitions shall apply:
 
      (i) Option Repurchase Price. "Option Repurchase Price" shall mean (A)
    the amount (if any) by which the Fair Market Value (as defined in
    Section 7(b)(iii)) of a single share of Ascend Common
 
                                      C-5
<PAGE>
 
    Stock as of the date of the applicable Repurchase Notice exceeds the
    per share Exercise Price, multiplied by (B) the number of shares of
    Ascend Common Stock purchasable pursuant to the Ascend Option or the
    portion thereof covered by the applicable Repurchase Notice.
 
      (ii) Share Repurchase Price. "Share Repurchase Price" shall mean the
    product of (A) the greater of (I) the Exercise Price paid by Cascade
    per share of Ascend Common Stock acquired pursuant to the Ascend Option
    and (II) the Fair Market Value (as defined in Section 7(b)(iii)) of a
    single share of Ascend Common Stock as of the date of the applicable
    Repurchase Notice, and (B) the number of shares of Ascend Common Stock
    to be repurchased pursuant to this Section 7 as covered by the
    applicable Repurchase Notice.
 
      (iii) Fair Market Value. As used in this Agreement, "Fair Market
    Value" shall mean, with respect to any security, the per share average
    of the last reported sale prices on The Nasdaq National Market (or such
    other national stock exchange or national market system as shall then
    be the primary trading market for such security) for the ten (10)
    trading days immediately preceding the applicable date.
 
    (c) Redelivery of Shares of Cascade Common Stock. In Ascend's discretion
  or if specified by Cascade in the Repurchase Notice, all or a portion of
  the Share Repurchase Price shall be paid by Ascend in shares of Cascade
  Common Stock, by redelivery to Cascade of the shares of Cascade Common
  Stock (and the certificate(s) representing such shares) previously
  delivered by Cascade to Ascend pursuant to a Stock Exercise. For purposes
  of this Section 7(c), each share of Cascade Common Stock redelivered to
  Cascade shall be valued at and exchanged for .546 shares of Cascade Common
  Stock. If fewer than all of the shares of Ascend Common Stock purchased by
  Cascade pursuant to a Stock Exercise are to be repurchased by Ascend
  pursuant to Section 7(a)(ii), Cascade shall issue to Ascend new
  certificates representing those shares of Cascade Common Stock which are
  not due to be redelivered to Cascade pursuant to this Section 7(c) to the
  extent that excess shares of Cascade Common Stock are included in the
  certificates redelivered to Cascade by Ascend. All shares of Cascade Common
  Stock redelivered to Cascade hereunder shall be free and clear of all
  claims, liens, charges, encumbrances and security interests of any nature
  whatsoever.
 
    (d) Payment and Redelivery of Ascend Options or Shares. In the event that
  Cascade exercises its rights under Section 7(a), Ascend shall, within ten
  (10) business days thereafter, pay the required amount to Cascade in
  immediately available funds (or shares of Cascade Common Stock, if
  applicable) and Cascade shall surrender to Ascend the Ascend Option or the
  certificate or certificates evidencing the shares of Ascend Common Stock
  purchased by Cascade pursuant hereto, and Cascade shall warrant that it has
  sole beneficial ownership of the Ascend Option or such shares and that the
  Ascend Option or such shares are then free and clear of all claims, liens,
  charges, encumbrances and security interests of any nature whatsoever.
 
    (e) Repurchase Price Reduced at Cascade's Option. In the event that
  payment of the repurchase price specified in Section 7(a) would subject the
  repurchase of the Ascend Option or the shares of Ascend Common Stock
  purchased by Cascade pursuant to the Ascend Option to a vote of the
  stockholders of Ascend pursuant to applicable law, regulations, or
  requirements of a national securities exchange or national market system or
  the Ascend Charter, then Cascade may, at its election, reduce the
  repurchase price or the number of shares covered by the Cascade repurchase
  request to an amount which would permit such repurchase without the
  necessity for such a vote.
 
  Section 8. Restrictions on Transfer.
 
    (a) Restrictions on Transfer. Prior to the fifth anniversary of the date
  hereof (the "Expiration Date"), neither party shall, directly or
  indirectly, by operation of law or otherwise, sell, assign, pledge, or
  otherwise dispose of or transfer any shares of capital stock of the other
  party acquired by such party pursuant to this Agreement, including any
  shares of Cascade Common Stock issued pursuant to a Stock Exercise
  ("Restricted Shares") or otherwise beneficially owned (within the meaning
  of Rule 13d-3 promulgated under the Exchange Act) by such other party,
  other than (i) pursuant to Section 7 or (ii) in accordance with Sections
  8(b) or 9.
 
                                      C-6
<PAGE>
 
    (b) Permitted Sales. Following the termination of the Merger Agreement, a
  party shall be permitted to sell any Restricted Shares beneficially owned
  by it if such sale is made (i) pursuant to a tender or exchange offer or
  other business combination transaction that has been approved or
  recommended, or otherwise determined to be fair to and in the best
  interests of the holders of common stock of the other party, by a majority
  of the members of the Board of Directors of such other party, or (ii)
  subject to Section 8(c) or (d) as the case may be, to a person who,
  immediately following such sale, would beneficially own (within the meaning
  of Rule 13d-3 promulgated under the Exchange Act), either alone or as part
  of a "group" (as used in Rule 13d-5 under the Exchange Act), not more than
  ten percent (10%) of such party's outstanding voting securities, which
  person is a passive institutional investor who would be eligible under Rule
  13d-1(b)(1) under the Exchange Act to report such holdings of Restricted
  Shares on Schedule 13G under the Exchange Act.
 
    (c) Ascend's Right of First Refusal. At any time after the first
  occurrence of a Trigger Event and prior to the Expiration Date, if Cascade
  shall desire to sell, assign, transfer or otherwise dispose of all or any
  of the shares of Ascend Common Stock or other securities acquired by it
  pursuant to the Ascend Option, it shall give Ascend written notice of the
  proposed transaction (a "Cascade Offer Notice"), identifying the proposed
  transferee, accompanied by a copy of a binding offer to purchase such
  shares or other securities signed by such transferee and setting forth the
  terms of the proposed transaction. A Cascade Offer Notice shall be deemed
  an offer by Cascade to Ascend, which may be accepted within five (5)
  business days of the receipt of such Cascade Offer Notice, on the same
  terms and conditions and at the same price at which Cascade is proposing to
  transfer such shares or other securities to such transferee. The purchase
  of any such shares or other securities by Ascend shall be settled within
  five (5) business days of the date of the acceptance of the offer and the
  purchase price shall be paid to Cascade in immediately available funds. In
  the event of the failure or refusal of Ascend to purchase all the shares or
  other securities covered by a Cascade Offer Notice, Cascade may sell all,
  but not less than all, of such shares or other securities to the proposed
  transferee at no less than the price specified and on terms no more
  favorable to the transferee than those set forth in the Cascade Offer
  Notice as long as such sale is completed within ninety (90) days of the
  receipt by Ascend of the applicable Cascade Offer Notice; provided that the
  provisions of this sentence shall not limit the rights Cascade may
  otherwise have in the event Ascend has accepted the offer contained in the
  Cascade Offer Notice and wrongfully refuses to purchase the shares or other
  securities subject thereto. The requirements of this Section 8(c) shall not
  apply to (i) any disposition as a result of which the proposed transferee
  would own beneficially not more than three percent (3%) of the outstanding
  voting power of Ascend, (ii) any disposition of Ascend Common Stock or
  other securities by a person to whom Cascade has assigned its rights under
  the Ascend Option with the consent of Ascend, (iii) any sale by means of a
  public offering registered under the Securities Act, or (iv) any transfer
  to a wholly-owned subsidiary of Cascade which agrees in writing to be bound
  by the terms hereof.
 
    (d) Cascade's Right of First Refusal. At any time after the first
  occurrence of a Trigger Event and prior to the Expiration Date, if Ascend
  shall desire to sell, assign, transfer or otherwise dispose of all or any
  of the shares of Cascade Common Stock or other securities acquired by it
  pursuant to a Stock Exercise of the Ascend Option by Cascade, it shall give
  Cascade written notice of the proposed transaction (a "Ascend Offer
  Notice"), identifying the proposed transferee, accompanied by a copy of a
  binding offer to purchase such shares or other securities signed by such
  transferee and setting forth the terms of the proposed transaction. An
  Ascend Offer Notice shall be deemed an offer by Ascend to Cascade, which
  may be accepted within five (5) business days of the receipt of such Ascend
  Offer Notice, on the same terms and conditions and at the same price at
  which Ascend is proposing to transfer such shares or other securities to
  such transferee. The purchase of any such shares or other securities by
  Cascade shall be settled within five (5) business days of the date of the
  acceptance of the offer and the purchase price shall be paid to Ascend in
  immediately available funds. In the event of the failure or refusal of
  Cascade to purchase all the shares or other securities covered by a Ascend
  Offer Notice, Ascend may sell all, but not less than all, of such shares or
  other securities to the proposed transferee at no less than the price
  specified and on terms no more favorable to the transferee than those set
  forth in the Ascend Offer Notice as long as such sale is completed within
  ninety (90) days of the receipt by Cascade of the applicable Ascend Offer
  Notice; provided that the
 
                                      C-7
<PAGE>
 
  provisions of this sentence shall not limit the rights Ascend may otherwise
  have in the event Cascade has accepted the offer contained in the Ascend
  Offer Notice and wrongfully refuses to purchase the shares or other
  securities subject thereto. The requirements of this Section 8(d) shall not
  apply to (i) any disposition as a result of which the proposed transferee
  would own beneficially not more than three percent (3%) of the outstanding
  voting power of Cascade, (ii) any sale by means of a public offering
  registered under the Securities Act, or (iii) any transfer to a wholly-
  owned subsidiary of Ascend which agrees in writing to be bound by the terms
  hereof.
 
    (e) Additional Restrictions. Prior to any permitted sales of any
  Restricted Shares under Section 8(b)(ii), the holder thereof shall give
  written notice to the issuer of such Restricted Shares of its intention to
  effect such transfer. Each such notice shall describe the manner of the
  proposed transfer and, if requested by the issuer of such Restricted
  Shares, shall be accompanied by an opinion of counsel satisfactory to such
  issuer (it being agreed that each of Gray Cary Ware & Freidenrich and
  Testa, Hurwitz & Thibeault, LLP shall be satisfactory) to the effect that
  such sale may be effected without registration under the Securities Act and
  any applicable state securities laws. Each certificate for Restricted
  Shares transferred as above provided shall bear the legend set forth in
  Section 11, except that such certificate shall not bear such legend if (i)
  such transfer is in accordance with the provisions of Rule 144 (or any
  other rule permitting public sale without registration under the Securities
  Act) or (ii) the opinion of counsel referred to above is to the further
  effect that the transferee and any subsequent transferee would be entitled
  to transfer such securities in a public sale without registration under the
  Securities Act and any applicable state securities laws. The restrictions
  provided for in this Section 8(e) shall not apply to securities which are
  not required to bear the legend prescribed by Section 11 in accordance with
  the provisions of this Agreement. The foregoing restrictions on
  transferability shall terminate as to any particular shares when such
  shares shall have been effectively registered under the Securities Act and
  any applicable state securities laws and sold or otherwise disposed of in
  accordance with the registration statement covering such shares.
 
  Section 9. Registration Rights.
 
    (a) Procedure. Following the termination of the Merger Agreement, either
  party hereto that owns Restricted Shares (a "Holder") may by written notice
  (the "Registration Notice") to the other party (the "Registrant") request
  the Registrant to register under the Securities Act all or any part of the
  Restricted Shares acquired by such Holder pursuant to this Agreement (the
  "Registrable Securities") in order to permit the sale or other disposition
  of such shares pursuant to a bona fide firm commitment underwritten public
  offering, in which the Holder and the underwriters shall effect as wide a
  distribution of such Registrable Securities as is reasonably practicable
  and shall use their best efforts to prevent any person (including any
  "group" as used in Rule 13d-5 under the Exchange Act)) and its affiliates
  from purchasing through such offering Restricted Shares representing more
  than three percent (3%) of the outstanding shares of common stock of the
  Registrant on a fully diluted basis (a "Permitted Offering"). Any rights to
  require registration hereunder shall terminate with respect to any shares
  that may be sold pursuant to Rule 144(k) under the Securities Act.
 
    (b) Manager's Certificate. The managing underwriter shall be an
  investment banking firm of nationally recognized standing, and shall be
  selected by (i) the Registrant within ten (10) business days after receipt
  of a Registration Notice, subject to approval of the Holder (which approval
  shall not be unreasonably withheld, delayed or conditioned), or (ii) if
  Registrant fails to deliver notice (the "Registrant's Designation Notice")
  to Holder of such selection within ten (10) business days after receipt of
  a Registration Notice, then by Holder subject to the reasonable approval of
  Registrant (which approval shall not be unreasonably withheld, delayed or
  conditioned) (the "Manager"), and Holder shall deliver written notice (the
  "Holder's Designation Notice") of such selection within ten (10) business
  days after expiration of the ten (10) day period in which Registrant is
  entitled to give notice. The Registrant's Designation Notice or the
  Holder's Designation Notice, as the case may be, shall state that (i) the
  party delivering such notice and its proposed Manager have a good faith
  intention to commence promptly a Permitted Offering, and (ii) such proposed
  Manager in good faith believes that, based on the then-prevailing market
  conditions, it will be able to sell the Registrable Securities to the
  public in a Permitted Offering within one hundred twenty (120) days at a
  per share price equal to at least eighty percent (80%) of the then Fair
  Market Value of such shares.
 
                                      C-8
<PAGE>
 
    (c) First Refusal Right. The Registrant (and/or any person designated by
  the Registrant) shall thereupon have the option exercisable by written
  notice delivered to the Holder within five (5) business days after the
  receipt of the Registration Notice, irrevocably to agree to purchase all or
  any part of the Registrable Securities proposed to be so sold for cash at a
  price equal to the product of (i) the number of Registrable Securities to
  be so purchased by the Registrant and (ii) the then Fair Market Value of
  such shares.
 
    (d) Closing. Any purchase of Registrable Securities by the Registrant (or
  its designee) under Section 9(c) shall take place at a closing to be held
  at the principal executive offices of the Registrant or at the offices of
  its counsel at any reasonable date and time designated by the Registrant
  and/or such designee in such notice within twenty (20) business days after
  delivery of such notice, and any payment for the shares to be so purchased
  shall be made by delivery at the time of such closing in immediately
  available funds.
 
    (e) Certain Limitations. If the Registrant does not elect to exercise its
  option pursuant to Section 9(c) with respect to all Registrable Securities,
  it shall use its best efforts to effect, as promptly as practicable, the
  registration under the Securities Act of the unpurchased Registrable
  Securities proposed to be so sold; provided, however, that (i) neither
  party shall be entitled to demand more than an aggregate of two (2)
  effective registration statements hereunder, and (ii) the Registrant will
  not be required to file any such registration statement during any period
  of time (not to exceed sixty (60) days after such request in the case of
  clause (A) below or ninety (90) days after such request in the case of
  clauses (B) and (C) below) when (A) the Registrant is in possession of
  material non-public information which it reasonably believes would be
  detrimental to be disclosed at such time and, in the opinion of counsel to
  the Registrant, such information would be required to be disclosed if a
  registration statement were filed at that time; (B) the Registrant is
  required under the Securities Act to include audited financial statements
  for any period in such registration statement and such financial statements
  are not yet available for inclusion in such registration statement; or (C)
  the Registrant determines, in its reasonable judgment, that such
  registration would interfere with any financing, acquisition or other
  transaction involving the Registrant or any of its material subsidiaries
  and that such transaction is material to the Registrant and its
  subsidiaries taken as a whole. If consummation of the sale of any
  Registrable Securities pursuant to a registration hereunder does not occur
  within one hundred twenty (120) days after the effectiveness of the initial
  registration statement, the provisions of this Section 9 shall again be
  applicable to any proposed registration.
 
    (f) State Securities Laws. The Registrant shall use its reasonable best
  efforts to cause any Registrable Securities registered pursuant to this
  Section 9 to be qualified for sale under the securities laws of such states
  as the Holder may reasonably request and shall continue such registration
  or qualification in effect in such jurisdiction; provided, however, that
  the Registrant shall not be required to qualify to do business in, or
  consent to general service of process in, any jurisdiction by reason of
  this provision.
 
    (g) Obligations of Registrant. The Registrant shall provide to the
  underwriters such documentation (including certificates, opinions of
  counsel and "comfort" letters from auditors) as is customary in connection
  with underwritten public offerings as such underwriters may reasonably
  require. The registration rights set forth in this Section 9 are subject to
  the condition that the Holder shall provide the Registrant with such
  information with respect to its Registrable Securities, the plans for the
  distribution thereof, and such other information with respect to the Holder
  as, in the reasonable judgment of counsel for the Registrant, is necessary
  to enable the Registrant to include in such registration statement all
  material facts required to be disclosed with respect to a registration
  thereunder.
 
    (h) Indemnification. In connection with any registration effected under
  this Section 9, the parties agree (i) to indemnify each other and the
  underwriters in the customary manner, (ii) to enter into an underwriting
  agreement in form and substance customary for transactions of such type
  with the Manager and the other underwriters participating in such offering,
  and (iii) to take all further actions which shall be reasonably necessary
  to effect such registration and sale (including, if the Manager deems it
  necessary, participating in road-show presentations).
 
    (i) Inclusion of Additional Shares of Registrant. The Registrant shall be
  entitled to include (at its expense) additional shares of its common stock
  in a registration effected pursuant to this Section 10 only if
 
                                      C-9
<PAGE>
 
  and to the extent the Manager determines that such inclusion will not
  adversely affect the prospects for success of such offering.
 
  Section 10. Adjustment Upon Changes in Capitalization.
 
    (a) Without limiting any restriction on Ascend contained in this
  Agreement or in the Merger Agreement, in the event of any change in Ascend
  Common Stock by reason of any stock dividend, stock split, merger (other
  than the Merger), recapitalization, combination, exchange of shares or any
  similar transaction, the type and number of shares or securities subject to
  the Ascend Option, and the Exercise Price per share provided herein, shall
  be adjusted appropriately and proper provision shall be made in the
  agreements governing such transaction so that Cascade shall receive, upon
  exercise of the Ascend Option, the number and class of securities or
  property that Cascade would have received in respect of the shares of
  Ascend Common Stock issuable to Cascade if the Ascend Option had been
  exercised immediately prior to such event or the record date therefor, as
  applicable. In addition, without limiting any restriction on Ascend or
  Cascade contained in this Agreement or the Merger Agreement, in the event
  of any change in Ascend Common Stock or Cascade Common Stock by reason of
  any stock dividend, stock split, merger (other than the Merger)
  recapitalization, combination, exchange of shares or any similar
  transaction, equitable adjustment shall be made to the other provisions
  hereof to carry out the original intent of this Agreement.
 
    (b) In the event that Ascend shall enter into an agreement: (i) to
  consolidate with or merge into any person, other than Cascade or one of its
  subsidiaries, and shall not be the continuing or surviving corporation of
  such consolidation or merger; (ii) to permit any person, other than Cascade
  or one of its Subsidiaries, to merge into Ascend and Ascend shall be the
  continuing or surviving corporation, but, in connection with such merger,
  the then-outstanding shares of Ascend Common Stock shall be changed into or
  exchanged for stock or other securities of Ascend or any other person or
  cash or any other property; or (iii) to sell or otherwise transfer all or
  substantially all of its assets to any person, other than Cascade or one of
  its Subsidiaries, then, and in each such case, the agreement governing such
  transaction shall make proper provision so that upon the consummation of
  such transaction and upon the subsequent exercise of the Ascend Option,
  Cascade shall be entitled to receive, for each share of Ascend Common Stock
  with respect to which the Ascend Option has not theretofore been exercised,
  an amount of consideration in the form of and equal to the per share amount
  of consideration that would be received by the holder of one share of
  Ascend Common Stock (and, in the event of an election or similar
  arrangement with respect to the type of consideration to be received by the
  holders of Ascend Common Stock, subject to the foregoing, proper provision
  shall be made so that the holder of the Ascend Option would have the same
  election or similar rights as would the holder of the number of shares of
  Ascend Common Stock for which the Ascend Option is then exercisable).
 
  Section 11. Restrictive Legends. Each certificate representing shares of
Ascend Common Stock issued to Cascade hereunder, and shares of Cascade Common
Stock, if any, delivered to Ascend pursuant to a Stock Exercise, shall include
a legend in substantially the following form:
 
  THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
  UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR ANY STATE SECURITIES OR
  BLUE SKY LAWS, AND MAY BE REOFFERED OR SOLD ONLY IF SO REGISTERED OR IF AN
  EXEMPTION FROM SUCH REGISTRATION IS AVAILABLE. SUCH SECURITIES ARE ALSO
  SUBJECT TO ADDITIONAL RESTRICTIONS ON TRANSFER AS SET FORTH IN THE ASCEND
  STOCK OPTION AGREEMENT DATED AS OF MARCH 30, 1997, A COPY OF WHICH MAY BE
  OBTAINED FROM THE ISSUER UPON REQUEST.
 
  It is understood and agreed that (i) the reference to the resale
restrictions of the Securities Act and state securities or Blue Sky laws in
the foregoing legend shall be removed by delivery of substitute certificate(s)
without such reference if Cascade or Ascend, as the case may be, shall have
delivered to the other party a copy of a letter from the staff of the
Securities and Exchange Commission, or an opinion of counsel, in form and
 
                                     C-10
<PAGE>
 
substance reasonably satisfactory to the other party, to the effect that such
legend is not required for purposes of the Securities Act or such laws; (ii)
the reference to the provisions of this Agreement in the foregoing legend
shall be removed by delivery of substitute certificate(s) without such
reference if the shares have been sold or transferred in compliance with the
provisions of this Agreement and under circumstances that do not require the
retention of such reference; and (iii) the legend shall be removed in its
entirety if the conditions in the preceding clauses (i) and (ii) are both
satisfied. In addition, such certificates shall bear any other legend as may
be required by law. Certificates representing shares sold in a registered
public offering pursuant to Section 9 shall not be required to bear the legend
set forth in this Section 11.
 
  Section 12. Binding Effect; No Assignment; No Third-Party
Beneficiaries. This Agreement shall be binding upon and inure to the benefit
of the parties hereto and their respective successors and permitted assigns.
Except as expressly provided for in this Agreement, neither this Agreement nor
the rights or obligations of either party hereto are assignable, except by
operation of law, or with the written consent of the other party, and any such
attempted assignment in violation of this Agreement shall be void and of no
force or effect. Nothing contained in this Agreement, express or implied, is
intended to confer upon any person other than the parties hereto and their
respective permitted assigns any rights or remedies of any nature whatsoever.
Any Restricted Shares sold by a party in compliance with the provisions of
Section 9 shall, upon consummation of such sale, be free of the restrictions
imposed and the benefits provided with respect to such shares by this
Agreement.
 
  Section 13. Specific Performance. The parties hereto recognize and agree
that if for any reason any of the provisions of this Agreement are not
performed in accordance with their specific terms or are otherwise breached,
immediate and irreparable harm or injury would be caused for which money
damages would not be an adequate remedy. Accordingly, each party agrees that,
in addition to other remedies, whether at law or in equity, the other party
shall be entitled to an injunction to prevent or restrain any violation or
threatened violation of the provisions of this Agreement, and to enforce
specifically the terms and provisions hereof, in any court of the State of
Delaware or of the United States of America located in the State of Delaware.
In the event that any action should be brought in equity to enforce the
provisions of this Agreement, neither party will allege, and each party hereby
waives the defense, that there is an adequate remedy at law. Each party hereto
irrevocably and unconditionally consents and submits to the jurisdiction of
the courts of the State of Delaware and of the United States of America
located in the City of Wilmington in the State of Delaware for any actions,
suits or proceedings arising out of or relating to this Agreement and the
transactions contemplated hereby, and waives any objection to venue in any
such court therein.
 
  Section 14. Validity.
 
    (a) The invalidity or unenforceability of any provision of this Agreement
  shall not affect the validity or enforceability of the other provisions of
  this Agreement, which shall remain in full force and effect.
 
    (b) In the event any court or other governmental or regulatory authority
  holds any provisions of this Agreement to be null, void or unenforceable,
  the parties hereto shall negotiate in good faith the execution and delivery
  of an amendment to this Agreement in order, as nearly as possible, to
  effectuate, to the extent permitted by law, the intent of the parties
  hereto with respect to such provision and the economic effects thereof.
 
    (c) If for any reason any such court or other governmental or regulatory
  authority determines that Cascade is not permitted to acquire, or Ascend is
  not permitted to repurchase pursuant to Section 7, the full number of
  shares of Ascend Common Stock provided in this Agreement (as the same may
  be adjusted), it is the express intention of Ascend to allow Cascade to
  acquire or to require Ascend to repurchase such lesser number of shares as
  may be permissible without any other amendment or modification hereof.
 
    (d) Each party agrees that, should any court or other governmental or
  regulatory authority hold any provision of this Agreement or part hereof to
  be null, void or unenforceable, or order any party to take any action
  inconsistent herewith, or not take any action required herein, the other
  party shall not be entitled to specific performance of such provision or
  part hereof or to any other remedy, including but not limited to money
  damages, for breach hereof or of any other provision of this Agreement or
  part hereof as the result of such holding or order.
 
                                     C-11
<PAGE>
 
  Section 15. Notices. All notices and other communications hereunder shall be
in writing and shall be deemed given if (a) delivered personally, or (b) if
sent by overnight courier service (receipt confirmed in writing), or (c) if
delivered by facsimile transmission (with receipt confirmed), or (d) five (5)
days after being mailed by registered or certified mail (return receipt
requested) to the parties in each case to the following addresses (or at such
other address for a party as shall be specified by like notice):
 
  If to Ascend, to:
 
  Ascend Communications, Inc.
  One Ascend Plaza
  1701 Harbor Bay Parkway
  Alameda, CA 94502
  Facsimile No.: (510) 769-6001
  Attention: President
 
  with a copy to:
 
  Gray Cary Ware & Freidenrich
  A Professional Corporation
  400 Hamilton Avenue
  Palo Alto, CA 94301
  Facsimile No.: (415) 327-3699
  Attention: Gregory M. Gallo, Esq. &
            Rod J. Howard, Esq.
 
  If to Cascade, to:
 
  Cascade Communications Corp.
  5 Carlisle Road
  Westford, MA 01886
  Facsimile No.: (508) 692-1221
  Attention: President and Corporate Counsel
 
  with a copy to:
 
  Testa, Hurwitz & Thibeault, LLP
  High Street Tower
  125 High Street
  Boston, MA 02110
  Fax Number: (617) 248-7100
  Attention: John A. Meltaus, Esq.
 
  Section 16. Governing Law. This Agreement shall be governed by and
construed, and any controversy arising out of or otherwise relating to this
Agreement shall be determined, in accordance with the laws of the State of
Delaware applicable to agreements made and to be performed entirely within
such State and without regard to its choice of law principles. Each party
hereto consents and submits to the exclusive jurisdiction of the courts of the
State of Delaware and the courts of the United States located in such state
for the adjudication of any action, suit, proceeding, claim or dispute arising
out of or otherwise relating to this Agreement.
 
  Section 17. Interpretation. The headings contained in this Agreement are for
reference purposes and shall not affect in any way the meaning or
interpretation of the Agreement. When reference is made in this Agreement to a
Section, such reference shall be to a Section of this Agreement, unless
otherwise indicated. Whenever the words "include," "includes," or "including"
are used in this Agreement, they shall be deemed to be followed by the words
"without limitation." Whenever "or" is used in this Agreement it shall be
construed in the nonexclusive sense. The words "herein," "hereby," "hereof,"
"hereto," "hereunder" and words of similar import refer to this Agreement.
 
                                     C-12
<PAGE>
 
  Section 18. Counterparts; Effect. This Agreement may be executed in two or
more counterparts, each of which shall be deemed to be an original, but all of
which shall constitute one and the same agreement.
 
  Section 19. Expenses. Ascend shall pay all expenses, and any and all
federal, state and local taxes and other charges, that may be payable in
connection with the preparation, issuance and delivery of Ascend stock
certificates under Section 4 and any stock listing or stock quotation
application required to be filed by Ascend with respect to such shares, and
Cascade shall pay all expenses, and any and all federal, state and local taxes
and other charges, that may be payable in connection with the preparation,
issuance and delivery of Cascade stock certificates in connection with a Stock
Exercise and any stock listing or stock quotation application required to be
filed by Ascend with respect to such shares. A registration effected under
Section 9 shall be effected at the Registrant's expense, except for
underwriting discounts and commissions and the fees and the expenses of
counsel to the Holder. Subject to the foregoing, and except as otherwise
expressly provided herein or in the Merger Agreement, all other costs and
expenses incurred in connection with the transactions contemplated by this
Agreement shall be paid by the party incurring such expenses.
 
  Section 20. Amendments; Waiver. This Agreement may be amended by the parties
hereto and the terms and conditions hereof may be waived only by an instrument
in writing signed on behalf of each of the parties hereto, or, in the case of
a waiver, by an instrument signed on behalf of the party waiving compliance.
 
  Section 21. Extension of Time Periods. The time periods for exercises of
certain rights hereunder shall be extended (but in no event by more than six
(6) months): (a) to the extent necessary to obtain all governmental approvals
for the exercise of such rights, and for the expiration of all statutory
waiting periods; and (b) to the extent necessary to avoid any liability or
disgorgement of profits under Section 16(b) of the Exchange Act by reason of
such exercise.
 
  Section 22. Further Assurances. Each party agrees to execute and deliver all
such further documents and instruments and take all such further action as may
be necessary in order to consummate the transactions contemplated hereby.
 
  IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed by their respective duly authorized officers as of the date first
above written.
 
                                          Ascend Communications, Inc.
 
                                          By: /s/ ROBERT K. DAHL
                                             -----------------------------------
                                            Name:  Robert K. Dahl
                                            Title: Vice President, Finance and
                                                   Chief Financial Officer
 
                                          Cascade Communications Corp.

                                          By: /s/ DANIEL E. SMITH
                                             -----------------------------------
                                            Name:  Daniel E. Smith
                                            Title: President and Chief Executive
                                                   Officer
 
                                     C-13

<PAGE>
 
                                                                     EXHIBIT 3
                         CASCADE DIRECTOR AND OFFICER
 
                            STOCK VOTING AGREEMENT
 
  THIS CASCADE DIRECTOR AND OFFICER STOCK VOTING AGREEMENT ("Agreement" or
"Cascade Stock Voting Agreement") is made and entered into as of March  , 1997
by and between Ascend Communications, Inc., a Delaware corporation ("Ascend"),
and the undersigned director or officer (the "Holder") of Cascade
Communications Corp., a Delaware corporation ("Cascade").
 
                                   Recitals
 
  Ascend, Catskill Merger Corporation, a Delaware corporation and a wholly-
owned subsidiary of Ascend ("Sub"), and Cascade have entered into an Agreement
and Plan of Reorganization, dated as of March 30, 1997 (the "Merger
Agreement") providing for the merger of Sub with and into Cascade (the
"Merger"). As a result of the Merger, which is intended to qualify as a
reorganization within the meaning of Section 368(a) of the Internal Revenue
Code of 1986, as amended, and to be accounted for as a pooling of interests,
Cascade will become a wholly-owned subsidiary of Ascend and stockholders of
Cascade will become stockholders of Ascend. Holder is the holder of record and
the beneficial owner (as defined in Rule 13d-3 under the Securities Exchange
Act of 1934, as amended (the "Exchange Act")) of the number of shares of the
capital stock of Cascade indicated on the signature page of this Cascade Stock
Voting Agreement (the "Shares"). As a condition to its execution and delivery
of the Merger Agreement, Ascend has requested that Holder agree, and in
consideration, and to induce the execution and delivery, of the Merger
Agreement by Ascend, Holder is willing to agree to vote all shares of Cascade
capital stock owned by Holder so as to facilitate consummation of the Merger,
as more fully described below.
 
  NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained herein, and for other good and valuable consideration, the receipt
and sufficiency of which are hereby acknowledged, the parties agree as
follows:
 
                                   Agreement
 
  Section 1 Agreement to Vote Shares. At every meeting of the Cascade
stockholders called with respect to any of the following, and at any
adjournment thereof, and with respect to every action or approval by written
consent of Cascade stockholders solicited with respect to any of the
following, Holder shall vote the Shares and any shares of Cascade capital
stock that Holder purchases or otherwise acquires beneficial ownership of
after the date of this Cascade Stock Voting Agreement and prior to the
expiration or termination of this Cascade Stock Voting Agreement ("New
Shares"):
 
    (a) in favor of adoption of the Merger Agreement, as the same may be
  amended from time to time, and approval of the Merger and any proposal or
  action which would, or could reasonably be expected to, facilitate the
  Merger;
 
    (b) against approval of any proposal made in opposition to or competition
  with consummation of the Merger and the Merger Agreement; and
 
    (c) against any merger, consolidation or other business combination of
  Cascade with, sale of assets or stock of Cascade to, or reorganization or
  recapitalization involving Cascade with, any party other than Ascend or an
  affiliate of Ascend as contemplated by the Merger Agreement (any event
  described in clauses (b) or (c) hereinafter referred to as an "Opposing
  Proposal").
 
  Holder, as the holder of voting stock of Cascade, shall be present, in
person or by proxy, at all meetings of stockholders of Cascade so that all
Shares and New Shares are counted for the purposes of determining the presence
of a quorum at such meetings. This Cascade Stock Voting Agreement is intended
to bind Holder only
 
                                       1
<PAGE>
 
with respect to the specific matters set forth herein and solely in his or her
capacity as a stockholder, and shall not prohibit, limit or restrict in any
manner Holder from acting in Holder's capacity as an officer or director of
Cascade or exercising or observing Holder's fiduciary duties and
responsibilities as an officer or director of Cascade.
 
  Section 2 Irrevocable Proxy. Concurrently with the execution of this Cascade
Stock Voting Agreement, Holder agrees to deliver to Ascend a proxy in the form
attached hereto as Annex A (the "Proxy"), which shall be irrevocable to the
extent provided therein; provided, however, that the Proxy shall be revoked
upon expiration or termination of this Cascade Stock Voting Agreement in
accordance with its terms.
 
  Section 3 Representations, Warranties and Covenants of Holder. Holder hereby
represents, warrants and covenants to Ascend as follows:
 
    (a) Ownership of Shares. Holder (i) as of the date of this Agreement, is
  the holder of record and beneficial owner of the Shares free and clear of
  any liens, claims, options, charges or other encumbrances that would
  interfere with the voting of the Shares or the granting of any proxy with
  respect thereto, (ii) as of the date of this Agreement, does not
  beneficially own any shares of capital stock of Cascade other than the
  Shares (except to the extent that Holder currently disclaims beneficial
  ownership in accordance with applicable law) and (iii) has full power and
  authority to make, enter into, deliver and carry out the terms of this
  Cascade Stock Voting Agreement and the Proxy.
 
    (b) No Voting Trusts and Agreements. Between the date of this Agreement
  and the expiration or termination of this Agreement, Holder will not, and
  will not permit any entity under Holder's control to, deposit any shares of
  Cascade capital stock held by Holder or such entity in a voting trust or
  subject any shares of Cascade capital stock held by such Holder or such
  entity to any arrangement or agreement with respect to the voting of such
  shares of capital stock, other than agreements entered into with Ascend.
 
    (c) Validity; No Conflict. This Cascade Stock Voting Agreement
  constitutes the legal, valid and binding obligation of Holder. Neither the
  execution of this Cascade Stock Voting Agreement by Holder nor the
  consummation of the transactions contemplated herein will violate or result
  in a breach of (i) any provision of any trust, charter, partnership
  agreement or other charter document applicable to Holder, (ii) any
  agreement to which Holder is a party or by which Holder is bound, (iii) any
  decree, judgment or order to which Holder is subject, or (iv) any law or
  regulation now in effect applicable to Holder.
 
    (d) No Proxy Solicitations. Except as required by law, including without
  limitation actions which the Holder determines in reasonable good faith are
  required pursuant to Holder's fiduciary duties as an officer or director of
  Cascade and as otherwise contemplated by the last sentence of Section 1,
  between the date of this Agreement and the expiration or termination of
  this Cascade Stock Voting Agreement, Holder will not, and will not permit
  any entity under Holder's control, to (i) solicit proxies or become a
  "participant" in a "solicitation" (as such terms are defined in Rule 14A
  under the Exchange Act) with respect to an Opposing Proposal or assist any
  party in taking or planning any action which would compete with, restrain
  or otherwise serve to interfere with or inhibit the timely consummation of
  the Merger in accordance with the terms of the Merger Agreement, (ii)
  initiate a stockholders' vote or action by written consent of Cascade
  stockholders without a meeting with respect to an Opposing Proposal or
  (iii) become a member of a "group" (as such term is used in Section 13(d)
  of the Exchange Act) with respect to any voting securities of Cascade with
  respect to an Opposing Proposal.
 
  Section 4 Representations, Warranties and Covenants of Ascend. Ascend
represents, warrants and covenants to Holder as follows:
 
    (a) Due Authorization. This Cascade Stock Voting Agreement has been
  authorized by all necessary corporate action on the part of Ascend and has
  been duly executed by a duly authorized officer of Ascend.
 
    (b) Validity; No Conflict. This Cascade Stock Voting Agreement
  constitutes the legal, valid and binding obligation of Ascend. Neither the
  execution of this Cascade Stock Voting Agreement by Ascend nor the
  consummation of the transactions contemplated herein will violate or result
  in a breach of (i) any
 
                                       2
<PAGE>
 
  agreement to which Ascend is a party or by which Ascend is bound, (ii) any
  decree, judgment or order to which Ascend is subject, or (iii) any law or
  regulation now in effect applicable to Ascend.
 
  Section 5 Additional Documents. Holder and Ascend hereby covenant and agree
to execute and deliver any additional documents necessary or desirable, in the
reasonable opinion of Ascend's legal counsel or Holder, as the case may be, to
carry out the intent of this Cascade Stock Voting Agreement.
 
  Section 6 Consent and Waiver. Holder hereby gives any consent or waiver
reasonably required for the performance of Holder's obligations hereunder
solely in such Holder's capacity as a stockholder of Cascade.
 
  Section 7 Termination. Notwithstanding any other provision contained herein,
this Cascade Stock Voting Agreement and the Proxy, and all obligations of
Holder hereunder and thereunder, shall terminate upon the earlier of the
Effective Time (as defined in the Merger Agreement) or the expiration or
termination of the Merger Agreement.
 
  Section 8 Miscellaneous.
 
    (a) Severability. If any term, provision, covenant or restriction of this
  Cascade Stock Voting Agreement or the Proxy (i) is held by a court of
  competent jurisdiction to be invalid, void or unenforceable for any reason,
  or (ii) would preclude the Merger from qualifying as a reorganization
  within the meaning of Section 368(a) of the Internal Revenue Code of 1986,
  as amended, or prevent Ascend or Cascade from accounting for the business
  combination contemplated by the Merger Agreement as a pooling of interests,
  such term, provision, covenant or restriction shall be modified or voided,
  as may be necessary to achieve the intent of the parties to the extent
  possible, and the remainder of the terms, provisions, covenants and
  restrictions of this Cascade Stock Voting Agreement shall remain in full
  force and effect and shall in no way be affected, impaired or invalidated.
 
    (b) Binding Effect and Assignment. This Cascade Stock Voting Agreement
  and all of the provisions hereof shall be binding upon and inure to the
  benefit of the parties hereto and their respective successors and permitted
  assigns, but, except as otherwise specifically provided herein, neither
  this Cascade Stock Voting Agreement nor any of the rights, interests or
  obligations of the parties hereto may be assigned by either of the parties
  hereto without the prior written consent of the other, and any attempted
  assignment thereof without such consent shall be null and void.
 
    (c) Amendments and Modifications. This Cascade Stock Voting Agreement may
  not be modified, amended, altered or supplemented except upon the execution
  and delivery of a written agreement executed by the parties hereto.
 
    (d) Specific Performance; Injunctive Relief. The parties hereto
  acknowledge that Ascend will be irreparably harmed by a breach of any of
  the covenants or agreements of Holder set forth herein and that there will
  be no adequate remedy at law for such a breach. Therefore, it is agreed
  that, in addition to any other remedies which may be available to Ascend
  upon such breach, Ascend shall have the right to enforce such covenants and
  agreements by specific performance, injunctive relief or by any other means
  available to it at law or in equity.
 
    (e) Notices. All notices, requests, claims, demands and other
  communications hereunder shall be in writing and sufficient if delivered in
  person, by commercial overnight courier service, by confirmed telecopy, or
  sent by mail (registered or certified mail, postage prepaid, return receipt
  requested), to the respective parties as follows:
 
     If to Ascend:  Ascend
                    One Ascend Plaza 
                    1701 Harbor Bay Parkway
                    Alameda, CA 94502
                    (510) 747-2616
                    Attention: Chief Financial Officer
 
 
                                       3
<PAGE>
 
     If to Holder:To the address for notice set forth on the last page
     hereof.
 
     With a copy to: Cascade
                     5 Carlisle Road
                     Westford, MA 01886
                     (508) 692-9214
                     Attention: Chief Financial Officer
                     
     and to:         Gray Cary Ware & Freidenrich
                     A Professional Corporation
                     400 Hamilton Avenue
                     Palo Alto, CA 94301
                     Fax Number: 415-327-3699
                     Attention: Gregory M. Gallo, Esq.
                     & Rod J. Howard, Esq.
 
     and to:         Testa, Hurwitz & Thibeault, LLP
                     High Street Tower
                     125 High Street
                     Boston, MA 02110
                     Fax Number: 617-248-7100
                     Attention: John A. Meltaus, Esq. &
                     Debra A. Buxbaum, Esq.
 
  or to such other address as either party may have furnished to the other in
writing in accordance herewith, except that notices of change of address shall
only be effective upon receipt.
 
    (f) Governing Law. This Cascade Stock Voting Agreement shall be governed
  by, construed and enforced in accordance with the laws of the State of
  Delaware, without giving effect to principles of conflicts of law. Each
  party hereto irrevocably and unconditionally consents and submits to the
  jurisdiction of the courts of the State of Delaware and of the United
  States of America located in the State of Delaware for any actions, suits
  or proceedings arising out of or relating to this agreement and the
  transactions contemplated hereby.
 
    (g) Entire Agreement. This Cascade Stock Voting Agreement contains the
  entire understanding of the parties with respect to the subject matter
  hereof, and supersedes all prior negotiations and understandings between
  the parties with respect to such subject matter.
 
    (h) Counterparts. This Cascade Stock Voting Agreement may be executed in
  one or more counterparts, each of which shall be an original, but all of
  which together shall constitute one and the same instrument.
 
    (i) Effect of Headings. The section headings contained herein are for
  convenience only and shall not affect the construction or interpretation of
  this Cascade Stock Voting Agreement.
 
                 [Remainder of Page Intentionally Left Blank]
 
                                       4
<PAGE>
 
  IN WITNESS WHEREOF, the parties have caused this Cascade Stock Voting
Agreement to be duly executed on the day and year first above written.
 
                                          Ascend Communications, Inc.
 
                                          By: _________________________________
 
                                          Its: ________________________________
 
                                          Holder
 
                                          By: _________________________________
 
                                          Holder's Address for Notice:
 
                                          _____________________________________
 
                                          _____________________________________
 
                                          _____________________________________
 
                                          Number of Shares owned beneficially:
 
                                          _____________________________________
 
                                          Number of Shares owned of record
                                           (ifdifferent from above):
 
                                          _____________________________________
 
                                       5
<PAGE>
 
                                    ANNEX A
 
                               IRREVOCABLE PROXY
 
  The undersigned stockholder of Cascade Corp., a Delaware corporation
("Cascade"), hereby irrevocably appoints and constitutes the members of the
Board of Directors of Ascend, Inc., a Delaware corporation ("Ascend"), and
each of them (the "Proxyholders"), the agents and proxies of the undersigned,
with full power of substitution and resubstitution, to the full extent of the
undersigned's rights with respect to the shares of capital stock of Cascade
beneficially owned by the undersigned, and any and all other shares or
securities issued or issuable in respect thereof, or which the undersigned
otherwise acquires, on or after the date hereof and prior to the date this
proxy terminates (collectively, the "Shares"), to vote the Shares as follows:
 
    The agents and proxies named above are empowered at any time prior to the
  expiration or termination of this proxy to exercise all voting rights
  (including, without limitation, the power to execute and deliver written
  consents with respect to the Shares) of the undersigned at every special or
  adjourned meeting of Cascade stockholders (but not at any annual meeting of
  Cascade stockholders), and in every written consent in lieu of such a
  meeting, or otherwise,
 
    (a) in favor of (i) adoption of the Agreement and Plan of Reorganization
  by and among Ascend, Catskill Merger Corporation ("Sub"), and Cascade, dated
  as of March 30, 1997, as the same may be amended from time to time (the
  "Merger Agreement"), and (ii) approval of the merger of Sub with and into
  Cascade as contemplated by the Merger Agreement (the "Merger") and any
  proposal or action which would, or could reasonably be expected to,
  facilitate the Merger;
 
    (b) against approval of any proposal made in opposition to or competition
  with consummation of the Merger and the Merger Agreement;
 
    (c) against any merger, consolidation or other business combination of
  Cascade with, sale of assets or stock of Cascade to, or reorganization or
  recapitalization involving Cascade with, any party other than Ascend or an
  affiliate of Ascend as contemplated by the Merger Agreement.
 
  The Proxyholders may not exercise this proxy with respect to any other
matter. The undersigned may vote the Shares on all such other matters in
person or by proxy.
 
  The proxy granted by the undersigned to the Proxyholders hereby is granted
as of the date of this Irrevocable Proxy in order to secure the obligations of
the undersigned set forth in Section 1 of the Cascade Director and Officer
Stock Voting Agreement between the undersigned and Ascend, and is irrevocable
and coupled with an interest in such obligations and in the shares of capital
stock of Cascade to be exchanged pursuant the Merger Agreement. This proxy will
expire or terminate upon the expiration or termination of such Cascade Director
and Officer Stock Voting Agreement in accordance with its terms.
 
  Upon the execution hereof, all prior proxies given by the undersigned with
respect to the Shares are hereby revoked, and no subsequent proxies will be
given with respect to the Shares until such time as this proxy shall be
terminated in accordance with its terms, other than any proxy given or to be
given by the undersigned with respect to the 1997 Annual Meeting of Cascade
stockholders.
 
  Any obligation of the undersigned hereunder shall be binding upon the
successors and assigns of the undersigned. The undersigned authorizes the
Proxyholders to file this proxy and any substitution or revocation of
substitution with the Secretary of Cascade and with any Inspector of Elections
at any special meeting of the stockholders of Cascade.
 
                 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]
 
<PAGE>
 
  This proxy is irrevocable and shall survive the insolvency, incapacity, death
or liquidation of the undersigned.
 
Dated: March , 1997.
 
  Name of Holder: ____________________________________
 
  Signature of Holder: _______________________________
 
  Shares beneficially owned by Holder: _______________
 
  Shares owned of record by Holder: __________________

<PAGE>
 
                                                                     EXHIBIT 4
                          ASCEND DIRECTOR AND OFFICER
                            STOCK VOTING AGREEMENT
 
  THIS ASCEND DIRECTOR AND OFFICER STOCK VOTING AGREEMENT ("Agreement" or
"Ascend Stock Voting Agreement") is made and entered into as of March  , 1997
by and between Cascade Communications Corp., a Delaware corporation
("Cascade"), and the undersigned officer or director (the "Holder") of Ascend
Communications, Inc., a Delaware corporation ("Ascend").
 
                                   Recitals
 
  Cascade, Catskill Merger Corporation, a Delaware corporation and a wholly-
owned subsidiary of Ascend ("Sub"), and Ascend have entered into an Agreement
and Plan of Reorganization, dated as of March  , 1997 (the "Merger Agreement")
providing for the merger of Sub with and into Cascade (the "Merger"). As a
result of the Merger, which is intended to qualify as a reorganization within
the meaning of Section 368(a) of the Internal Revenue Code of 1986, as
amended, and to be accounted for as a pooling of interests, Cascade will
become a wholly-owned subsidiary of Ascend and stockholders of Cascade will
become stockholders of Ascend. Holder is the holder of record and the
beneficial owner (as defined in Rule 13d-3 under the Securities Exchange Act
of 1934, as amended, (the "Exchange Act")) of the number of shares of the
capital stock of Ascend indicated on the signature page of this Ascend Stock
Voting Agreement (the "Shares"). As a condition to its execution and delivery
of the Merger Agreement, Cascade has requested that Holder agree, and in
consideration, and to induce the execution and delivery, of the Merger
Agreement by Cascade, Holder is willing to agree to vote all shares of Ascend
capital stock owned by Holder so as to facilitate consummation of the Merger,
as more fully described below.
 
  NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained herein, and for other good and valuable consideration, the receipt
and sufficiency of which are hereby acknowledged, the parties agree as
follows:
 
                                   Agreement
 
  Section 1 Agreement to Vote Shares. At every meeting of the Ascend
stockholders called with respect to any of the following, and at any
adjournment thereof, and with respect to every action or approval by written
consent of Ascend stockholders solicited with respect to any of the following,
Holder shall vote the Shares and any shares of Ascend capital stock that
Holder purchases or otherwise acquires beneficial ownership of after the date
of this Ascend Stock Voting Agreement and prior to the expiration or
termination of this Ascend Stock Voting Agreement ("New Shares"):
 
    (a) in favor of approval of the issuance of shares of Ascend common stock
  pursuant to the Merger Agreement, as the same may be amended from time to
  time, and any proposal or action which would, or could reasonably be
  expected to, facilitate the Merger and the other transactions contemplated
  by the Merger Agreement;
 
    (b) against approval of any proposal made in opposition to or competition
  with consummation of the Merger and the Merger Agreement; and
 
    (c) against any merger, consolidation or other business combination of
  Ascend with, sale of assets or stock of Ascend to, or reorganization or
  recapitalization involving Ascend with, any party other than Cascade or an
  affiliate of Cascade as contemplated by the Merger Agreement (any event
  described in clause (b) or (c) hereafter referred to as an "Opposing
  Proposal").
 
  Holder, as the holder of voting stock of Ascend, shall be present, in person
or by proxy, at all meetings of stockholders of Ascend so that all Shares and
New Shares are counted for the purposes of determining the
 
                                       1
<PAGE>
 
presence of a quorum at such meetings. This Ascend Stock Voting Agreement is
intended to bind Holder only with respect to the specific matters set forth
herein and solely in his or her capacity as a stockholder, and shall not
prohibit, limit or restrict in any manner Holder from acting in Holder's
capacity as an officer or director of Ascend or exercising or observing
Holder's fiduciary duties and responsibilities as an officer or director of
Ascend.
 
  Section 2 Irrevocable Proxy. Concurrently with the execution of this Ascend
Stock Voting Agreement, Holder agrees to deliver to Cascade a proxy in the
form attached hereto as Annex A (the "Proxy"), which shall be irrevocable to
the extent provided therein; provided, however, that the Proxy shall be
revoked upon expiration or termination of this Ascend Stock Voting Agreement
in accordance with its terms.
 
  Section 3 Representations, Warranties and Covenants of Holder. Holder hereby
represents, warrants and covenants to Cascade as follows:
 
    (a) Ownership of Shares. Holder (i) as of the date of this Agreement, is
  the holder of record and beneficial owner of the Shares free and clear of
  any liens, claims, options, charges or other encumbrances that would
  interfere with the voting of the Shares or the granting of any proxy with
  respect thereto, (ii) as of the date of this Agreement, does not
  beneficially own any shares of capital stock of Ascend other than the
  Shares (except to the extent that Holder currently disclaims beneficial
  ownership in accordance with applicable law) and (iii) has full power and
  authority to make, enter into, deliver and carry out the terms of this
  Ascend Stock Voting Agreement and the Proxy.
 
    (b) No Voting Trusts and Agreements. Between the date of this Agreement
  and the expiration or termination of this Agreement, Holder will not, and
  will not permit any entity under Holder's control to, deposit any shares of
  Ascend capital stock held by Holder or such entity in a voting trust or
  subject any shares of Ascend capital stock held by such Holder or such
  entity to any arrangement or agreement with respect to the voting of such
  shares of capital stock, other than agreements entered into with Cascade.
 
    (c) Validity; No Conflict. This Ascend Stock Voting Agreement constitutes
  the legal, valid and binding obligation of Holder. Neither the execution of
  this Ascend Stock Voting Agreement by Holder nor the consummation of the
  transactions contemplated herein will violate or result in a breach of (i)
  any provision of any trust, charter, partnership agreement or other charter
  document applicable to Holder, (ii) any agreement to which Holder is a
  party or by which Holder is bound, (iii) any decree, judgment or order to
  which Holder is subject, or (iv) any law or regulation now in effect
  applicable to Holder.
 
    (d) No Proxy Solicitations. Except as required by law, including, without
  limitation, actions which the Holder determines in reasonable good faith
  are required pursuant to Holder's fiduciary duties as an officer or
  director of Ascend, and as otherwise contemplated by the last sentence of
  Section 1, between the date of this Agreement and the expiration or
  termination of this Agreement, Holder will not, and will not permit any
  entity under Holder's control, to (i) solicit proxies or become a
  "participant" in a "solicitation" (as such terms are defined in Rule 14A
  under the Exchange Act) with respect to an Opposing Proposal or assist any
  party in taking or planning any action which would compete with, restrain
  or otherwise serve to interfere with or inhibit the timely consummation of
  the Merger in accordance with the terms of the Merger Agreement, (ii)
  initiate a stockholders' vote or action by written consent of Ascend
  stockholders without a meeting with respect to an Opposing Proposal or
  (iii) become a member of a "group" (as such term is used in Section 13(d)
  of the Exchange Act) with respect to any voting securities of Ascend with
  respect to an Opposing Proposal.
 
  Section 4 Representations, Warranties and Covenants of Cascade. Cascade
represents, warrants and covenants to Holder as follows:
 
    (a) Due Authorization. This Ascend Stock Voting Agreement has been
  authorized by all necessary corporate action on the part of Cascade and has
  been duly executed by a duly authorized officer of Cascade.
 
    (b) Validity; No Conflict. This Ascend Stock Voting Agreement constitutes
  the legal, valid and binding obligation of Cascade. Neither the execution
  of this Ascend Stock Voting Agreement by Cascade
 
                                       2
<PAGE>
 
  nor the consummation of the transactions contemplated herein will violate
  or result in a breach of (i) any agreement to which Cascade is a party or
  by which Cascade is bound, (ii) any decree, judgment or order to which
  Cascade is subject, or (iii) any law or regulation now in effect applicable
  to Cascade.
 
  Section 5 Additional Documents. Holder and Cascade hereby covenant and agree
to execute and deliver any additional documents necessary or desirable, in the
reasonable opinion of Cascade's legal counsel or Holder, as the case may be,
to carry out the intent of this Ascend Stock Voting Agreement.
 
  Section 6 Consent and Waiver. Holder hereby gives any consent or waiver
reasonably required for the performance of Holder's obligations hereunder
solely in such Holder's capacity as a stockholder of Cascade.
 
  Section 7 Termination. Notwithstanding any other provision contained herein,
this Ascend Stock Voting Agreement and the Proxy, and all obligations of
Holder hereunder and thereunder, shall terminate upon the earlier of the
Effective Time (as defined in the Merger Agreement) or the expiration or
termination of the Merger Agreement.
 
  Section 8 Miscellaneous.
 
    (a) Severability. If any term, provision, covenant or restriction of this
  Ascend Stock Voting Agreement or the Proxy (i) is held by a court of
  competent jurisdiction to be invalid, void or unenforceable for any reason,
  or (ii) would preclude the Merger from qualifying as a reorganization
  within the meaning of Section 368(a) of the Internal Revenue Code of 1986,
  as amended, or prevent Cascade or Ascend from accounting for the business
  combination contemplated by the Merger Agreement as a pooling of interests,
  such term, provision, covenant or restriction shall be modified or voided,
  as may be necessary to achieve the intent of the parties to the extent
  possible, and the remainder of the terms, provisions, covenants and
  restrictions of this Ascend Stock Voting Agreement shall remain in full
  force and effect and shall in no way be affected, impaired or invalidated.
 
    (b) Binding Effect and Assignment. This Ascend Stock Voting Agreement and
  all of the provisions hereof shall be binding upon and inure to the benefit
  of the parties hereto and their respective successors and permitted
  assigns, but, except as otherwise specifically provided herein, neither
  this Ascend Stock Voting Agreement nor any of the rights, interests or
  obligations of the parties hereto may be assigned by either of the parties
  hereto without the prior written consent of the other, and any attempted
  assignment thereof without such consent shall be null and void.
 
    (c) Amendments and Modifications. This Ascend Stock Voting Agreement may
  not be modified, amended, altered or supplemented except upon the execution
  and delivery of a written agreement executed by the parties hereto.
 
    (d) Specific Performance; Injunctive Relief. The parties hereto
  acknowledge that Cascade will be irreparably harmed by a breach of any of
  the covenants or agreements of Holder set forth herein and that there will
  be no adequate remedy at law for such a breach. Therefore, it is agreed
  that, in addition to any other remedies which may be available to Cascade
  upon such breach, Cascade shall have the right to enforce such covenants
  and agreements by specific performance, injunctive relief or by any other
  means available to it at law or in equity.
 
    (e) Notices. All notices, requests, claims, demands and other
  communications hereunder shall be in writing and sufficient if delivered in
  person, by commercial overnight courier service, by confirmed telecopy, or
  sent by mail (registered or certified mail, postage prepaid, return receipt
  requested), to the respective parties as follows:
 
     If to Cascade:      Cascade Communications Corp.
                         5 Carlisle Road
                         Westford, MA 01886
                         Fax Number: 508-692-9214
                         Attention: Chief Financial Officer
 
                                       3
<PAGE>
 
     If to Holder: To the address for notice set forth on the last page
     hereof.
 
     With a copy to:     Ascend Communications, Inc.
                         One Ascend Plaza
                         1701 Harbor Bay Parkway
                         Alameda, CA 94502
                         Fax Number: 510-747-94502
                         Attention: Chief Financial Officer

 
     and to:             Gray Cary Ware & Freidenrich
                         A Professional Corporation
                         400 Hamilton Avenue
                         Palo Alto, CA 94301
                         Fax Number: 415-327-3699 Attention: Gregory M. Gallo,
                         Esq. & Rod J. Howard, Esq.
 
     and to:             Testa, Hurwitz & Thibeault, LLP
                         High Street Tower
                         125 High Street
                         Boston, MA 02110
                         Fax Number: 617-248-7100
                         Attention: John A. Meltaus, Esq. and Debra A.
                         Buxbaum, Esq.
 
  or to such other address as either party may have furnished to the other in
writing in accordance herewith, except that notices of change of address shall
only be effective upon receipt.
 
    (f) Governing Law. This Ascend Stock Voting Agreement shall be governed
  by, construed and enforced in accordance with the laws of the State of
  Delaware, without giving effect to principles of conflicts of law. Each
  party hereto irrevocably and unconditionally consents and submits to the
  jurisdiction of the courts of the State of Delaware and of the United
  States of America located in the State of Delaware for any actions, suits
  or proceedings arising out of or relating to this agreement and the
  transactions contemplated hereby.
 
    (g) Entire Agreement. This Ascend Stock Voting Agreement contains the
  entire understanding of the parties with respect to the subject matter
  hereof, and supersedes all prior negotiations and understandings between
  the parties with respect to such subject matter.
 
    (h) Counterparts. This Ascend Stock Voting Agreement may be executed in
  one or more counterparts, each of which shall be an original, but all of
  which together shall constitute one and the same instrument.
 
    (i) Effect of Headings. The section headings contained herein are for
  convenience only and shall not affect the construction or interpretation of
  this Ascend Stock Voting Agreement.
 
                   [REST OF PAGE INTENTIONALLY LEFT BLANK.]
 
 
                                       4
<PAGE>
 
  IN WITNESS WHEREOF, the parties have caused this Ascend Stock Voting
Agreement to be duly executed on the day and year first above written.
 
                                          Cascade Communications Corp.
 
                                          By: _________________________________
 
                                          Its: ________________________________
 
                                          Holder
 
                                          By: _________________________________
 
                                          Holder's Address for Notice:
 
                                          _____________________________________
 
                                          _____________________________________
 
                                          _____________________________________
 
                                          Number of Shares owned beneficially:
 
                                          _____________________________________
 
                                          Number of Shares owned of record
                                           (if different from above):
 
                                          _____________________________________
 
                                       5
<PAGE>
 
                                    ANNEX A
 
                               IRREVOCABLE PROXY
 
  The undersigned stockholder of Ascend Communications, Inc., a Delaware
corporation ("Ascend"), hereby irrevocably appoints and constitutes the
members of the Board of Directors of Cascade Communications Corp., a Delaware
corporation ("Cascade"), and each of them (the "Proxyholders"), the agents and
proxies of the undersigned, with full power of substitution and
resubstitution, to the full extent of the undersigned's rights with respect to
the shares of capital stock of Ascend beneficially owned by the undersigned,
and any and all other shares or securities issued or issuable in respect
thereof, or which the undersigned otherwise acquires, on or after the date
hereof and prior to the date this proxy terminates (collectively, the
"Shares"), to vote the Shares as follows:
 
    The agents and proxies named above are empowered at any time prior to the
  expiration or termination of this proxy to exercise all voting rights
  (including, without limitation, the power to execute and deliver written
  consents with respect to the Shares) of the undersigned at every special or
  adjourned meeting of Ascend stockholders, and in every written consent in
  lieu of such a meeting, or otherwise,
 
    (a) in favor of approval of (i) the issuance of shares of Ascend common
  stock pursuant to the Agreement and Plan of Reorganization by and among
  Ascend, Catskill Merger Corporation ("Sub"), and Cascade dated as of March
  30, 1997, as the same may be amended from time to time (the "Merger
  Agreement"), and (ii) any proposal or action which would, or could
  reasonably be expected to, facilitate the merger of Sub with and into
  Cascade pursuant to the Merger Agreement (the "Merger") and the other
  transactions contemplated by the Merger Agreement;
 
    (b) against approval of any proposal made in opposition to or competition
  with consummation of the Merger and the Merger Agreement; and
 
    (c) against any merger, consolidation or other business combination of
  Ascend with, sale of assets or stock of Ascend to, or reorganization or
  recapitalization involving Ascend with, any party other than Cascade or an
  affiliate of Cascade, as contemplated by the Merger Agreement.
 
  The Proxyholders may not exercise this proxy with respect to any other
matter. The undersigned may vote the Shares on all such other matters.
 
  The proxy granted by the undersigned to the Proxyholders hereby is granted as
of the date of this Irrevocable Proxy in order to secure the obligations of the
undersigned set forth in Section 1 of the Ascend Director and Officer Stock
Voting Agreement between the undersigned and Cascade, and is irrevocable and
coupled with an interest in such obligations. This proxy will terminate upon the
expiration or termination of such Ascend Director and Officer Stock Voting
Agreement in accordance with its terms.
 
  Upon the execution hereof, all prior proxies given by the undersigned with
respect to the Shares are hereby revoked, and no subsequent proxies will be
given with respect to the Shares until such time as this proxy shall be
terminated in accordance with its terms.
 
  Any obligation of the undersigned hereunder shall be binding upon the
successors and assigns of the undersigned. The undersigned authorizes the
Proxyholders to file this proxy and any substitution or revocation of
substitution with the Secretary of Ascend and with any Inspector of Elections
at any meeting of the stockholders of Ascend.
 
                   [REST OF PAGE INTENTIONALLY LEFT BLANK.]
<PAGE>
 
  This proxy is irrevocable and shall survive the insolvency, incapacity, death
or liquidation of the undersigned.
 
  Dated: March  , 1997.
 
  Name of Holder: ____________________________________
 
  Signature of Holder: _______________________________
 
  Shares beneficially owned by Holder: _______________
 
  Shares owned of record by Holder: __________________

<PAGE>
 
                                                                     EXHIBIT 5
 
              CASCADE DIRECTOR, OFFICER AND STOCKHOLDER AGREEMENT
 
  THIS CASCADE DIRECTOR, OFFICER AND STOCKHOLDER AGREEMENT ("Agreement") is
made and entered into as of March  , 1997 by and among Ascend Communications,
Inc., a Delaware corporation ("Ascend"), and the undersigned director, officer
and/or stockholder ("Signatory") of Cascade Communications Corp., a Delaware
corporation ("Cascade") . Capitalized terms not otherwise defined herein shall
have the meanings ascribed to them in the Merger Agreement (as defined below).
 
                                   Recitals
 
  Ascend and Cascade have entered into an Agreement and Plan of
Reorganization, dated as of March 30, 1997 (the "Merger Agreement"), pursuant
to which Cascade will become a wholly-owned subsidiary of Ascend and the
stockholders of Cascade will become stockholders of Ascend. It will be a
condition to the effectiveness of the Merger that (i) legal counsel to Cascade
and Ascend will have delivered their respective opinions to the effect that
the Merger will constitute a reorganization within the meaning of Section
368(a) of the Internal Revenue Code of 1986, as amended (the "Code"), and (ii)
the independent auditing firms that audit the annual financial statements of
Cascade and Ascend will have delivered letters confirming the appropriateness
of pooling of interests accounting for the Merger under Accounting Principles
Board Opinion No. 16 and the applicable regulations of the Securities and
Exchange Commission (the "Commission"). The execution and delivery of this
Agreement by Signatory is a material inducement to Ascend to enter into the
Merger Agreement. Signatory has been advised that Signatory may be deemed to
be an "affiliate" of Cascade, as such term is used (i) for purposes of
paragraphs (c) and (d) of Rule 145 of the Commission under the Securities Act
of 1933, as amended (the "Act"), and/or (ii) in the Commission's Accounting
Series Releases 130 and 135, as amended, it being understood that nothing
contained herein shall be construed as an admission by Signatory that
Signatory is in fact an affiliate of Cascade.
 
  NOW, THEREFORE, intending to be legally bound, the parties hereby agree as
follows:
 
                                   Agreement
 
  1. Acknowledgments by Signatory. Signatory acknowledges and understands that
the covenants made by Signatory set forth herein will be relied upon by
Ascend, Cascade, and their respective affiliates, legal counsel and auditing
firms, and that substantial losses and damages may be incurred by such persons
if Signatory's representations and warranties are inaccurate or if Signatory's
covenants and agreements are breached. Signatory has carefully read this
Agreement and the Merger Agreement and has consulted with such legal counsel
and financial advisers as Signatory has deemed appropriate in connection with,
and prior to, the execution and delivery of this Agreement.
 
  2. Compliance with Rule 145 and the Act.
 
  (a) Signatory has been advised that (i) the issuance of shares of Ascend
Common Stock in connection with the Merger is expected to be effected pursuant
to a Registration Statement filed by Ascend on Form S-4, and the resale of
such shares will be subject to the restrictions set forth in Rule 145 under
the Act unless such shares are otherwise transferred pursuant to an effective
registration statement under the Act or an appropriate exemption from
registration, and (ii) Signatory may be deemed to be an affiliate of Cascade.
Signatory accordingly agrees not to sell, pledge, transfer or otherwise
dispose of any shares of Ascend Common Stock issued to Signatory in the
Merger, unless (i) such sale, pledge, transfer or other disposition is made in
conformity with the requirements of Rule 145 under the Act, (ii) such sale,
pledge, transfer or other disposition is made pursuant to an effective
registration statement under the Act, or (iii) Signatory delivers to Ascend a
written opinion of counsel, in form and substance reasonably acceptable to
Ascend, to the effect that such sale, pledge, transfer or other disposition is
otherwise exempt from registration under the Act.
 
  (b) Ascend will give stop transfer instructions to its transfer agent with
respect to any Ascend Common Stock received by Signatory pursuant to the
Merger, and there will be placed on the certificates representing such Ascend
Common Stock, or any substitutions therefor, a legend stating in substance as
follows:
 
                                       1
<PAGE>
 
    "THE SHARES REPRESENTED BY THIS CERTIFICATE WERE ISSUED PURSUANT TO A
  BUSINESS COMBINATION WHICH IS BEING ACCOUNTED FOR AS A POOLING OF
  INTERESTS, IN A TRANSACTION TO WHICH RULE 145 PROMULGATED UNDER THE
  SECURITIES ACT OF 1933 APPLIES, AND MAY ONLY BE TRANSFERRED IN CONFORMITY
  WITH RULE 145, PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT, OR IN
  ACCORDANCE WITH A WRITTEN OPINION OF COUNSEL, REASONABLY ACCEPTABLE TO THE
  ISSUER IN FORM AND SUBSTANCE TO THE EFFECT THAT SUCH TRANSFER IS EXEMPT
  FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933. SUCH SHARES MAY NOT BE
  TRANSFERRED UNTIL SUCH TIME AS ASCEND SHALL HAVE PUBLISHED FINANCIAL
  RESULTS COVERING AT LEAST 30 DAYS OF COMBINED OPERATIONS WITH CASCADE. THE
  SHARES REPRESENTED BY THIS CERTIFICATE MAY NOT BE OFFERED, SOLD, PLEDGED,
  TRANSFERRED OR OTHERWISE DISPOSED OF EXCEPT IN ACCORDANCE WITH THE TERMS OF
  A CERTAIN DIRECTOR, OFFICER AND STOCKHOLDER AGREEMENT DATED AS OF MARCH  ,
  1997 BETWEEN THE HOLDER OF THIS CERTIFICATE AND ASCEND, A COPY OF WHICH
  AGREEMENT MAY BE INSPECTED BY THE HOLDER OF THIS CERTIFICATE AT THE
  PRINCIPAL OFFICES OF ASCEND OR FURNISHED BY ASCEND TO THE HOLDER OF THIS
  CERTIFICATE UPON WRITTEN REQUEST AND WITHOUT CHARGE."
 
  The legend set forth above shall be removed (by delivery of a substitute
certificate without such legend), and Ascend shall so instruct its transfer
agent, if a registration statement respecting the sale of the shares has been
declared effective under the Act or if Signatory delivers to Ascend (i)
satisfactory written evidence that the shares have been sold in compliance
with Rule 145 (in which case, the substitute certificate will be issued in the
name of the transferee), or (ii) an opinion of counsel, in form and substance
reasonably acceptable to Ascend, to the effect that sale of the shares by the
holder thereof is no longer subject to Rule 145.
 
  3.  Covenants Related to Pooling of Interests.
 
  (a) During the period beginning on the date thirty (30) days prior to the
Closing Date (as defined in the Merger Agreement) and ending on the day after
Ascend has published (within the meaning of Accounting Series Release No. 135)
financial results covering at least thirty (30) days of post-Merger combined
operations of Ascend and Cascade (the "Restricted Period") in the form of a
quarterly earnings report, an effective registration statement filed with the
Commission, a report to the Commission on Form 10-K, 10-Q or 8-K or any other
public filing or announcement which includes the combined results of
operations, Signatory will not sell, exchange, transfer, pledge, distribute,
or otherwise dispose of or grant any option, establish any "short" or put-
equivalent position with respect to or enter into any similar transaction
(through derivatives or otherwise) intended to have or having the effect,
directly or indirectly, of reducing Signatory's risk relative to (i) any
shares of Cascade Common Stock or Ascend Common Stock owned by Signatory or
(ii) any shares of Ascend Common Stock received by Signatory in connection
with the Merger.
 
  (b) Notwithstanding anything to the contrary contained in Section 3(a),
Signatory will be permitted, during the Restricted Period, to sell, exchange,
transfer, pledge, distribute or otherwise dispose of or grant any option,
establish any "short" or put-equivalent position with respect to or enter into
any similar transaction (through derivatives or otherwise) intended to have or
having the effect, directly or indirectly, of reducing Signatory's risk
relative to any shares of Cascade Common Stock or Ascend Common Stock received
by Signatory in connection with the Merger an amount of such shares not more
than the de minimis amount permitted by the Commission in its rules and
releases relating to pooling-of-interests accounting treatment, subject to the
advance concurrence of Ascend and Cascade and each of their independent
auditors.
 
  4. Miscellaneous.
 
  (a) This Agreement may be executed in one or more counterparts, each of
which shall be deemed to be an original, but all of which together shall
constitute one and the same document.
 
  (b) This Agreement shall be enforceable by, and shall inure to the benefit
of and be binding upon, the parties hereto and their respective successors and
assigns.
 
                                       2
<PAGE>
 
  (c) This Agreement shall be governed by and construed, interpreted and
enforced in accordance with the internal laws of the State of Delaware,
applicable to agreements made and performed wholly within such state. Each
party hereto irrevocably and unconditionally consents and submits to the
jurisdiction of the courts of the State of Delaware and of the United States
of America located in the State of Delaware for any actions, suits or
proceedings arising out of or relating to this Agreement and the transactions
contemplated hereby.
 
  (d) If any provision of this Agreement is held to be unenforceable for any
reason, it shall be modified rather than voided, if possible, in order to
achieve the intent of the parties to the extent possible. In any event, all
other provisions of this Agreement shall be deemed valid and enforceable to
the extent possible.
 
  (e) Legal counsel to and auditors for the parties to the Merger Agreement
shall be entitled to rely upon this Agreement to the extent they deem
necessary.
 
  (f) This Agreement shall not be modified or amended, or any right hereunder
waived or any obligation excused, except by a written agreement signed by both
parties.
 
  (g) Notwithstanding any other provision contained herein, this Agreement and
all obligations hereunder shall terminate upon the termination of the Merger
Agreement in accordance with its terms.
 
  (h) From and after the Effective Time of the Merger and as long as is
necessary in order to permit Signatory to sell Ascend Common Stock held by
Signatory pursuant to Rule 145 and, to the extent applicable, Rule 144 under
the Securities Act, Ascend shall use all reasonable efforts to file on a
timely basis all reports required to be filed by it pursuant to the Securities
Exchange Act of 1934, as amended, and the rules and regulations thereunder, as
the same shall be in effect at the time, and shall otherwise use all
reasonable efforts to make available adequate public information regarding
Ascend in such manner as may be required to satisfy the requirements of
paragraph (c) of Rule 144 under the Securities Act.
 
  IN WITNESS WHEREOF, this Agreement is executed as of the date first shown
above.
 
                                          Ascend Communications, Inc. a
                                           Delaware corporation
 
 
                                          By:__________________________________
 
                                          Signatory
 
 
                                          By:__________________________________
 
                                          Name of Signatory:___________________
 
                                          Title of Signatory (if applicable):__
 
                                          Number of Shares Owned:______________
 
                                          Number of Shares Issuable
                                          uponExercise of Stock Options:_______
 
                                       3

<PAGE>
 
                                                                     EXHIBIT 6
 
              ASCEND DIRECTOR, OFFICER AND STOCKHOLDER AGREEMENT
 
  THIS ASCEND DIRECTOR, OFFICER AND STOCKHOLDER AGREEMENT ("Agreement") is
made and entered into as of March  , 1997 by and among Ascend Communications,
Inc., a Delaware corporation ("Ascend"), Cascade Communications Corp., a
Delaware corporation ("Cascade") and the undersigned director, officer and/or
stockholder ("Signatory") of Ascend. Capitalized terms not otherwise defined
herein shall have the meanings ascribed to them in the Merger Agreement (as
defined below).
 
                                   Recitals
 
  Ascend and Cascade have entered into an Agreement and Plan of Reorganization
dated as of March 30, 1997 (the "Merger Agreement") pursuant to which Cascade
will become a wholly-owned subsidiary of Ascend, and stockholders of Cascade
will become stockholders of Ascend. It will be a condition to the effectiveness
of the Merger that the independent auditing firms that audit the annual
financial statements of Ascend and Cascade will have delivered letters
confirming their concurrence with Ascend's management as to the appropriateness
of pooling of interests accounting for the Merger under Accounting Principles
Board Opinion No. 16 and the applicable regulations of the Securities and
Exchange Commission (the "Commission"). The execution and delivery of this
Agreement by Signatory is a material inducement to Ascend to enter into the
Merger Agreement. Signatory has been advised that Signatory may be deemed to be
an "affiliate" of Ascend, as such term is used in Accounting Series Releases 130
and 135, as amended, of the Commission, it being understood that nothing
contained herein shall be construed as an admission by Signatory that Signatory
is in fact an affiliate of Ascend.
 
  NOW, THEREFORE, intending to be legally bound, the parties hereby agree as
follows:
 
                                   Agreement
 
  1. Acknowledgment. Signatory acknowledges and understands that the
representations, warranties and covenants by Signatory set forth herein will
be relied upon by Ascend, Cascade and their respective affiliates, legal counsel
and auditing firms, and that substantial losses and damages may be incurred by
these persons if Signatory's representations and warranties are inaccurate or if
Signatory's covenants and agreements are breached. Signatory has carefully read
this Agreement and the Merger Agreement and has consulted with such legal
counsel and financial advisers as Signatory has deemed necessary in connection
with, and prior to, the execution and delivery of this Agreement.
 
  2. Covenants Related to Pooling of Interests. During the period beginning on
the earlier of the date thirty (30) days prior to the anticipated Closing Date
(as defined in the Merger Agreement or such date as set forth in a notice to
be delivered by Ascend to Signatory) and ending on the day two days after the
day that Ascend has published (within the meaning of Accounting Series Release
No. 135) financial results covering at least thirty (30) days of post-Merger
combined operations of Ascend and Cascade (the "Restricted Period"), in the
form of a quarterly earnings report, an effective registration statement filed
with the Commission, a report to the Commission on Form 10-K, 10-Q or 8-K or
any other public filing or announcement which includes the combined results of
operations, Signatory will not sell, exchange, transfer, pledge, distribute,
make any gift or otherwise dispose of or grant any option, establish any
"short" or put-equivalent position with respect to or enter into any similar
transaction (through derivatives or otherwise) intended to have or having the
effect, directly or indirectly, of reducing Signatory's risk relative to any
shares of Ascend Common Stock. Ascend may, at its discretion, place a stock
transfer notice consistent with the foregoing with its transfer agent with
respect to Signatory's shares. Notwithstanding the foregoing, Signatory will
be permitted, during the Restricted Period, to sell, exchange, transfer,
pledge, distribute, make any gift or otherwise dispose of or grant any option,
establish any "short" or put-equivalent position with respect to or enter into
any similar transaction (through derivatives or otherwise) intended to have or
having the effect, directly or indirectly, of reducing Signatory's risk
relative to an amount of shares of Ascend Common Stock not more than the de
minimis amount permitted by the Commission in its rules and releases relating
to pooling-of-interests accounting treatment, subject to the advance
concurrence of Ascend and Cascade and each of their independent auditors.
 
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  3. Beneficial Ownership of Stock. Except for the Ascend Common Stock and
options to purchase Ascend Common Stock set forth in Appendix A hereto,
Signatory does not beneficially own any shares of Ascend Common Stock or any
other equity securities of Ascend or any options, warrants or other rights to
acquire any equity securities of Ascend.
 
  4. Reliance by Third Parties. Legal counsel to and auditors for the parties
to the Merger Agreement shall be entitled to rely upon this Agreement to the
extent they deem necessary.
 
  5. Miscellaneous. For the convenience of the parties hereto, this Agreement
may be executed in one or more counterparts, each of which shall be deemed to
be an original, but all of which together shall constitute one and the same
document. This Agreement shall be enforceable by, and shall inure to the
benefit of and be binding upon, the parties hereto and their respective
successors and assigns. This Agreement shall be governed by and construed,
interpreted and enforced in accordance with the internal laws of the State of
Delaware applicable to agreements made and performed wholly within such state.
 
  Each party hereto irrevocably and unconditionally consents and submits to
the jurisdiction of the courts of the State of Delaware and of the United
States of America located in the State of Delaware for any actions, suits or
proceedings arising out of or relating to this Agreement and the transactions
contemplated hereby. If any provision of this Agreement is held to be
unenforceable for any reason, it shall be modified rather than voided, if
possible, in order to achieve the intent of the parties to the extent
possible. In any event, all other provisions of this Agreement shall be deemed
valid and enforceable to the extent possible. This Agreement shall not be
modified and amended, or any right hereunder waived or any obligation excused,
except by a written agreement signed by both parties.
 
  Executed as of the date shown on the first page of this Agreement.
 
Ascend Communications, Inc. a             Signatory
 Delaware corporation
 
 
 
                                          By:__________________________________
 
 
By:__________________________________
 
                                          Print Name of Signatory:_____________
 
Name:________________________________
 
                                          Title (if applicable):_______________
Title:_______________________________
 
Cascade Communications Corp. a
 Delaware corporation
 
 
By:__________________________________
 
Name:________________________________
 
Title:_______________________________
 
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                                   APPENDIX A
 
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