Leading Research Firms Name Sonus Networks Number One Provider of Carrier-Class Packet Voice Solutions

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Cahners In-Stat, Infonetics and Synergy Research Group Name Sonus #1 for Third Consecutive Quarter; Company Maintains Commanding Lead in Packet Voice Market

WESTFORD, Mass., June 4, 2001 – Sonus Networks (Nasdaq: SONS) today announced that it has been ranked the worldwide market share leader for carrier-class packet voice switching equipment for the first quarter of 2001. Reports issued recently by industry research firms Cahners In-Stat Group, Infonetics Research and Synergy Research Group confirm Sonus' continued leadership position in a number of market segments.

"We continued to make tremendous progress with our customers in the first quarter, expanding our deployments with current carrier customers and forging relationships with new customers," commented Stephen Collins, vice president, marketing, Sonus Networks. "We are extremely gratified to again be recognized by these highly respected research firms for our leading industry position." 

Cahners In-Stat Group released its first quarter market share report last week, with data showing Sonus as continued leader in purpose-built carrier VoIP gateways, in both ports and revenues. Based on the numbers in the Cahners report, Sonus continued to outpace other players in the industry, while competitors' shares were flat or declined in the last quarter. 

"Sonus continues to ramp its voice gateway port shipments from one quarter to the next even in a difficult telecom service provider environment in which many other firms find their shipments declining," said Norm Bogen, director, WAN Infrastructure and Services, Cahners In-Stat Group.

In May, Infonetics Research issued its quarterly worldwide market share and forecast service, and named Sonus number one in next generation voice/data switch revenues. In this report, Infonetics noted that Sonus continued to expand its lead over its nearest competitors, growing its market share by an additional 15 percent from the previous quarter.

"While we believe overall service provider capital expenditures will experience a short period of decline during 2001, we are seeing a shift from legacy TDM equipment to next-gen voice products," said Michael Howard, principal analyst and co-founder, Infonetics Research. "Sonus is well positioned to benefit from this shift, and this is borne out by the fact that Sonus continued to expand its market leadership in the first quarter, capturing 66% of next-gen voice/data switch revenues."

Synergy Research Group also named Sonus the leader in its quarterly report on voice over IP (VoIP) equipment market share. Synergy ranked Sonus number one in several market segments including: total worldwide VoIP port shipments; service provider VoIP gateway port shipments; high density VoIP gateway revenues and port shipments; and combined high density VoIP/Internet Call Diversion revenues.  

"Sonus made considerable headway during the first quarter of the year," noted Jeremy Duke, founder and principal analyst, Synergy Research Group. "Sonus is the vendor gaining traction in the market, and this momentum is clearly reflected in its market share across a number of segments."  

Sonus delivers a complete family of carrier-class, packet voice infrastructure solutions for the new public network. The company's award-winning solutions include the GSX9000 Open Services Switch, the PSX6000 SoftSwitch, the INtelligentIP Softswitch, the SGX2000 SS7 Signaling Gateway, and Sonus Insight Element Management System. These solutions combine to form a system that delivers the scalability, reliability, interconnectivity and voice quality required for deployment in global service provider networks. Moreover, the comprehensive Sonus solution offers a powerful and open platform upon which carriers can build new revenue streams through the rapid development and delivery of innovative voice and data services.    

About Sonus Networks

Sonus Networks, Inc. is a leading provider of voice infrastructure products for the new public network. Sonus' solutions enable service providers to deploy an integrated network capable of carrying both voice and data traffic, and to deliver a range of innovative, new services. The Sonus Open Services Architecture (OSA) and award-winning Packet Telephony suite cut the time-to-market for competitive new service products, allowing carriers and third-party developers to expand marketshare and build important new revenue streams. Its highly scalable products fully interoperate with and extend the life and utility of today's public network. Sonus embodies in its management and staff decades of experience in developing carrier-class voice, data and multimedia solutions for implementation in the world's largest networks. 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' Annual Report on Form 10-K, dated March 28, 2001, 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 Company's ability to grow its customer base, dependence on new product offerings, market acceptance of its products, rapid technological and market change, integration risks relating to the acquisition of telecom technologies and manufacturing and sourcing risks.

GSX9000, PSX6000, SGX2000 and Open Services Architecture are trademarks of Sonus Networks. INtelligentIP is a registered trademark of Sonus Networks. All other company and product names may be trademarks of the respective companies with which they are associated.