<Page>
EXHIBIT 99.1
FOR IMMEDIATE RELEASE
For more information, please contact:
Investor Relations: Media Relations:
Jocelyn Lynds Beth Morrissey
978-589-8672 978-589-8579
jlynds@sonusnet.com bmorrissey@sonusnet.com
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SONUS NETWORKS REPORTS 2002 SECOND QUARTER FINANCIAL RESULTS
WESTFORD, MASS., JULY 11, 2002 -Sonus Networks, Inc. (Nasdaq: SONS), a leading
provider of voice infrastructure solutions for the new public network, today
reported its financial results for the second quarter ended June 30, 2002.
Revenues for the second quarter of fiscal 2002 were $21.3 million compared with
$52.6 million in the same period last year. Adjusted net loss for the second
quarter of fiscal 2002 was $10.5 million or $0.06 per share compared with
adjusted net income for the second quarter of fiscal 2001 of $1.2 million or
$0.01 per share. Actual net loss for the second quarter of fiscal 2002 was $17.8
million or $0.09 per share compared with an actual net loss for the second
quarter of fiscal 2001 of $51.4 million or $0.30 per share.
Revenues for the first six months of fiscal 2002 were $42.5 million compared
with $94.1 million in the same period last year. Adjusted net loss for the first
six months of fiscal 2002 was $23.2 million or $0.12 per share compared with
adjusted net income for the first six months of fiscal 2001 of $1.3 million or
$0.01 per share. Actual net loss for the first six months of fiscal 2002 was
$34.0 million or $0.18 per share compared with an actual net loss for the first
six months of fiscal 2001 of $133.9 million or $0.80 per share.
A reconciliation of adjusted to actual net income (loss) for the periods is as
follows:
<Table>
<Caption>
THREE MONTHS ENDED SIX MONTHS ENDED
($ Millions) JUNE 30, JUNE 30,
--------------------------------------
2002 2001 2002 2001
---- ---- ---- ----
Adjusted net income (loss) ($10.5) $ 1.2 ($23.2) $ 1.3
Write-off of inventory and purchase commitments -- -- (9.4) --
Stock-based compensation (6.0) (13.9) (11.7) (29.3)
Amortization of goodwill and purchased intangibles (0.3) (38.7) (0.8) (65.9)
Restructuring benefit (charges), net (1.0) -- 11.1 --
In-process research and development -- -- -- (40.0)
------ ------ ------ -------
Actual net income (loss) ($17.8) ($51.4) ($34.0) ($133.9)
====== ====== ====== =======
</Table>
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Sonus Networks Reports 2002 Second Quarter Financial Results -- p.2/
"The telecommunications market remains very challenging, and continues to impact
our financial results," said Hassan Ahmed, president and CEO, Sonus Networks.
"During this period, we have been focused on managing our business and finances
with precision and extending our market leadership. Today's announcement of
Deutsche Telekom, the largest PTT in Europe, as our newest customer further
validates the packet voice market, and is an important endorsement of Sonus and
our packet voice solutions."
Concurrent with this release, Sonus announced that Deutsche Telekom's T-Systems
International division has chosen Sonus to build out its next-generation VoIP
network to provide multi-national corporations with enhanced voice services (see
today's press release "T-Systems International Selects Sonus Networks to Provide
Packet Voice Infrastructure and Services"). T-Systems will leverage the
Sonus-based network to deliver services such as global voice VPN (virtual
private network) and sophisticated call center routing facilities, with
additional services to follow.
In May, Sonus announced that KDDI, one of the largest carriers in Japan,
selected Sonus to provide packet voice infrastructure solutions to support the
delivery of voice over IP (VoIP) services over KDDI's broadband network. By
deploying Sonus' industry-leading media gateway, softswitch and management
solutions, KDDI will be able to cost-effectively deliver a range of SIP-based
voice services over its high-speed fiber optic infrastructure.
During the quarter, Sonus unveiled its SMARRT(TM) Cable solution, a
next-generation packet voice solution specifically geared to the requirements of
cable operators (MSOs). Building on packet technology already proven in carrier
voice networks, Sonus' SMARRT Cable solution is designed for carrier-grade
reliability, voice quality and features, and delivers voice services in a
cost-effective and flexible PacketCable(TM) architecture.
To further drive the implementation of VoIP in broadband cable networks, Sonus
and Motorola, Inc. Broadband Communications Sector are collaborating to create a
comprehensive packet voice solution available for broadband network operators.
The Motorola/Sonus end-to-end packet voice solution draws upon the extensive
capabilities of two industry leaders - Motorola providing advanced IP access
network solutions and Sonus providing telco-grade packet voice infrastructure
products.
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Sonus Networks Reports 2002 Second Quarter Financial Results -- p.3/
Also in the quarter, Sonus was named the worldwide market share leader for
carrier-class packet voice equipment for the seventh consecutive quarter.
Leading industry research firms In-Stat/MDR, Infonetics Research and Synergy
Research Group issued first quarter 2002 market share reports confirming Sonus'
continued leadership position in a number of market segments. Also in May, the
Aberdeen Group released a report citing Sonus' deployment with Japanese carrier
Fusion Communications as one of the most significant VoIP deployments of 2001.
Today, Sonus announced that it has been named as a defendant in a securities
class action lawsuit (STEINBERG V. SONUS NETWORKS, INC., ET AL., 02 CV 11315 D.
Mass) alleging that the company made false and misleading statements about its
products and business. Sonus has not yet filed a response to the complaint. The
company believes that the claims are without merit and that it has substantial
legal and factual defenses, which it intends to pursue vigorously.
ABOUT SONUS NETWORKS
Sonus Networks, Inc., is a leading provider of packet voice infrastructure
products for the new public network. With its Open Services Architecture(TM)
(OSA), Sonus delivers end-to-end solutions addressing a full range of carrier
applications, including trunking, residential access and Centrex, tandem
switching, and IP voice termination, as well as enhanced services. Sonus'
award-winning voice infrastructure solutions, including media gateways,
softswitches and network management systems, are deployed in service provider
networks worldwide. Sonus, founded in 1997, is headquartered in Westford,
Massachusetts. Additional information on Sonus is available at
http://www.sonusnet.com.
This release may contain projections or other forward-looking statements
regarding future events or the future financial performance of Sonus that
involve risks and uncertainties. Readers are cautioned that these
forward-looking statements are only predictions and may differ materially from
actual future events or results. Readers are referred to Sonus' Quarterly Report
on Form 10-Q, dated May 10, 2002 and filed with the SEC, which identifies
important risk factors that could cause actual results to differ from those
contained in the forward-looking statements. These risk factors include, among
others, the adverse effect of recent developments in the telecommunications
industry, the weakened financial position of many emerging service providers,
Sonus' ability to grow its customer base, dependence on new product offerings,
market acceptance of its products, rapid technological and market change and
manufacturing and sourcing risks.
SMARRT AND OPEN SERVICES ARCHITECTURE ARE TRADEMARKS OF SONUS NETWORKS. ALL
OTHER COMPANY AND PRODUCT NAMES MAY BE TRADEMARKS OF THE RESPECTIVE COMPANIES
WITH WHICH THEY ARE ASSOCIATED.
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Sonus Networks Reports 2002 Second Quarter Financial Results -- p.4/
SONUS NETWORKS, INC.
CONDENSED CONSOLIDATED BALANCE SHEETS
(IN THOUSANDS)
<Table>
<Caption>
JUNE 30, DECEMBER 31,
2002 2001
--------- ---------
(UNAUDITED)
ASSETS
CURRENT ASSETS:
Cash, cash equivalents and marketable securities $ 104,710 $ 125,067
Accounts receivable, net 6,448 9,440
Inventories 9,847 18,865
Other current assets 1,804 2,952
--------- ---------
Total current assets 122,809 156,324
PROPERTY AND EQUIPMENT, NET 16,978 23,335
GOODWILL, NET 1,673 1,673
PURCHASED INTANGIBLE ASSETS, NET 2,074 2,863
OTHER ASSETS, NET 561 689
--------- ---------
$ 144,095 $ 184,884
========= =========
LIABILITIES AND STOCKHOLDERS' EQUITY
CURRENT LIABILITIES:
Accounts payable and accrued expenses $ 31,968 $ 36,301
Accrued restructuring expenses 5,083 8,596
Deferred revenue 11,310 13,349
Current portion of long-term obligations 848 1,055
--------- ---------
Total current liabilities 49,209 59,301
LONG-TERM OBLIGATIONS, LESS CURRENT PORTION 2,037 12,698
CONVERTIBLE SUBORDINATED NOTES 10,000 10,000
STOCKHOLDERS' EQUITY:
Common stock 206 205
Capital in excess of par value 861,042 860,883
Accumulated deficit (763,410) (729,398)
Deferred compensation (14,786) (28,721)
Treasury stock (203) (84)
--------- ---------
Total stockholders' equity 82,849 102,885
--------- ---------
$ 144,095 $ 184,884
========= =========
</Table>
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Sonus Networks Reports 2002 Second Quarter Financial Results -- p.5/
SONUS NETWORKS, INC.
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
(IN THOUSANDS, EXCEPT PER SHARE DATA)
(UNAUDITED)
<Table>
<Caption>
THREE MONTHS ENDED JUNE 30, 2002
------------------------------------
ACTUAL ADJUSTED
RESULTS ADJUSTMENTS RESULTS (A)
--------- ------- --------
REVENUES $ 21,295 $ -- $ 21,295
Cost of revenues 9,948 -- 9,948
--------- ------- --------
GROSS PROFIT 11,347 -- 11,347
OPERATING EXPENSES:
Research and development 12,225 -- 12,225
Sales and marketing 8,280 -- 8,280
General and administrative 1,690 -- 1,690
Stock-based compensation 5,950 (5,950) --
Amortization of goodwill and purchased intangible assets 383 (383) --
Restructuring charges, net 1,013 (1,013) --
--------- ------- --------
Total operating expenses 29,541 (7,346) 22,195
--------- ------- --------
LOSS FROM OPERATIONS (18,194) 7,346 (10,848)
Interest expense (136) -- (136)
Interest income 512 -- 512
--------- ------- --------
NET LOSS $ (17,818) $ 7,346 $(10,472)
========= ======= ========
BASIC AND DILUTED NET LOSS PER SHARE $ (0.09) $ (0.06)
========= ========
SHARES USED IN COMPUTATION 189,193 189,193
========= ========
</Table>
<Table>
<Caption>
THREE MONTHS ENDED JUNE 30, 2001
------------------------------------
ACTUAL ADJUSTED
RESULTS ADJUSTMENTS RESULTS (A)
--------- ------- --------
REVENUES $ 52,551 $ -- $ 52,551
Cost of revenues 22,160 -- 22,160
--------- ------- --------
GROSS PROFIT 30,391 -- 30,391
OPERATING EXPENSES:
Research and development 16,697 -- 16,697
Sales and marketing 10,615 -- 10,615
General and administrative 3,279 -- 3,279
Stock-based compensation 13,847 (13,847) --
Amortization of goodwill and purchased intangible assets 38,704 (38,704) --
--------- ------- --------
Total operating expenses 83,142 (52,551) 30,591
--------- ------- --------
LOSS FROM OPERATIONS (52,751) 52,551 (200)
Interest expense (113) -- (113)
Interest income 1,473 -- 1,473
--------- ------- --------
NET INCOME (LOSS) $ (51,391) $52,551 $ 1,160
========= ======= ========
BASIC AND DILUTED NET INCOME (LOSS) PER SHARE $ (0.30) $ 0.01 (B)
========= ========
SHARES USED IN COMPUTATION 171,329 214,971 (B)
========= ========
</Table>
(A) These Adjusted Condensed Consolidated Statements of Operations are for
informational purposes only and are not in accordance with US generally
accepted accounting principles. These statements exclude the impact of the
amortization of stock-based compensation, amortization of goodwill and
purchased intangibles and restructuring charges.
(B) Represents only diluted net income per share as calculated under the
treasury stock method.
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<Page>
Sonus Networks Reports 2002 Second Quarter Financial Results -- p.6/
SONUS NETWORKS, INC.
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
(IN THOUSANDS, EXCEPT PER SHARE DATA)
(UNAUDITED)
<Table>
<Caption>
SIX MONTHS ENDED JUNE 30, 2002
----------------------------------------------
ACTUAL ADJUSTED
RESULTS ADJUSTMENTS RESULTS (A)
---------- -------- ----------
REVENUES $ 42,453 $ -- $ 42,453
Cost of revenues:
Write-off of inventory and purchase commitments 9,434 (9,434) --
Other cost of revenues 19,823 -- 19,823
---------- -------- ----------
Total cost of revenues 29,257 (9,434) 19,823
---------- -------- ----------
GROSS PROFIT 13,196 9,434 22,630
OPERATING EXPENSES:
Research and development 26,840 -- 26,840
Sales and marketing 16,687 -- 16,687
General and administrative 3,156 -- 3,156
Stock-based compensation 11,693 (11,693) --
Amortization of goodwill and purchased intangible assets 789 (789) --
Restructuring charges (benefit), net (11,128) 11,128 --
---------- -------- ----------
Total operating expenses 48,037 (1,354) 46,683
LOSS FROM OPERATIONS (34,841) 10,788 (24,053)
Interest expense (275) -- (275)
Interest income 1,104 -- 1,104
---------- -------- ----------
NET LOSS $ (34,012) $ 10,788 $ (23,224)
========== ======== ==========
BASIC AND DILUTED NET LOSS PER SHARE $ (0.18) $ (0.12)
========== ==========
SHARES USED IN COMPUTATION 187,593 187,593
========== ==========
</Table>
<Table>
<Caption>
SIX MONTHS ENDED JUNE 30, 2002
----------------------------------------------
ACTUAL ADJUSTED
RESULTS ADJUSTMENTS RESULTS (A)
---------- -------- ----------
REVENUES $ 94,050 $ -- $ 94,050
Cost of revenues 40,171 -- 40,171
---------- -------- ----------
GROSS PROFIT 53,879 -- 53,879
OPERATING EXPENSES:
Research and development 30,616 -- 30,616
Sales and marketing 19,103 -- 19,103
General and administrative 5,942 -- 5,942
Stock-based compensation 29,270 (29,270) --
Amortization of goodwill and purchased intangible assets 65,911 (65,911) --
In-process research and development 40,000 (40,000) --
---------- -------- ----------
Total operating expenses 190,842 (135,181) 55,661
LOSS FROM OPERATIONS (136,963) 135,181 (1,782)
Interest expense (281) -- (281)
Interest income 3,374 -- 3,374
---------- -------- ----------
NET INCOME (LOSS) $ (133,870) $135,181 $ 1,311
========== ======== ==========
BASIC AND DILUTED NET INCOME (LOSS) PER SHARE $ (0.80) $ 0.01 (B)
========== ==========
SHARES USED IN COMPUTATION 166,689 210,902 (B)
========== ==========
</Table>
(A) These Adjusted Condensed Consolidated Statements of Operations are for
informational purposes only and are not in accordance with US generally
accepted accounting principles. These statements exclude the impact of the
write-off of inventory and purchase commitments, amortization of
stock-based compensation, amortization of goodwill and purchased
intangibles, restructuring charges (benefit) and in-process research and
development expenses.
(B) Represents only diluted net income per share as calculated under the
treasury stock method.
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