<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE SONUS
NETWORKS, INC. CONDENSED CONSOLIDATED BALANCE SHEET AS OF SEPTEMBER 30, 2000
(UNAUDITED) AND THE STATEMENT OF OPERATIONS FOR THE NINE MONTHS ENDED SEPTEMBER
30, 2000 (UNAUDITED) AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 9-MOS
<FISCAL-YEAR-END> DEC-31-2000
<PERIOD-START> JAN-01-2000
<PERIOD-END> SEP-30-2000
<CASH> 152,685
<SECURITIES> 0
<RECEIVABLES> 8,317
<ALLOWANCES> (700)
<INVENTORY> 14,388
<CURRENT-ASSETS> 176,569
<PP&E> 15,459
<DEPRECIATION> (4,756)
<TOTAL-ASSETS> 188,183
<CURRENT-LIABILITIES> 37,827
<BONDS> 0
0
0
<COMMON> 184
<OTHER-SE> 150,172
<TOTAL-LIABILITY-AND-EQUITY> 188,183
<SALES> 23,171
<TOTAL-REVENUES> 23,171
<CGS> 14,846
<TOTAL-COSTS> 14,846
<OTHER-EXPENSES> 55,904
<LOSS-PROVISION> 0
<INTEREST-EXPENSE> 209
<INCOME-PRETAX> (43,766)
<INCOME-TAX> 0
<INCOME-CONTINUING> (43,766)
<DISCONTINUED> 0
<EXTRAORDINARY> 0
<CHANGES> 0
<NET-INCOME> (43,766)
<EPS-BASIC> (0.57)
<EPS-DILUTED> (0.57)
</TABLE>