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Cahners In-Stat/MDR, Infonetics Research and Synergy Research Group Rank Sonus Market Share Leader for Q4 and Full Year 2001

WESTFORD, Mass., February 25, 2002 – Sonus Networks (Nasdaq: SONS) today announced that it continues to increase its leadership position in the market for carrier-class packet voice equipment, and has been ranked the worldwide market share leader for a sixth consecutive quarter. Reports issued by industry research firms Cahners In-Stat/MDR, Infonetics Research and Synergy Research Group verified Sonus' expanded leadership position in a number of market segments for the fourth quarter of 2001, as well as for the full calendar year.

"The latest reports from Cahners, Infonetics and Synergy underscore Sonus' position as the vendor of choice for packet voice solutions among leading carriers and service providers," said Terri Griffin, vice president, marketing, Sonus Networks. "Our increased market share in a number of these segments is a testament to the steadfast dedication of the Sonus team to deliver the highest levels of technical innovation, product quality and customer service in the packet voice industry."

Data from Cahners In-Stat/MDR's quarterly market share report identified Sonus as the leader in purpose-built carrier voice over IP (VoIP) gateways, in both port shipments and revenues, as well as the leader in total voice over packet (VoP) gateway ports shipped in all product segments. According to the Cahners report, Sonus expanded its lead in the last quarter and continued to maintain its steady lead over competitors in these categories throughout the year.

"Carrier confidence in Sonus' products is demonstrated by how the company consistently wins business over its competition," said Norm Bogen, director, WAN Infrastructure and Services, Cahners In-Stat/MDR. "Sonus continues to dominate high-density voice gateways, even with the challenging market dynamics we've seen in the service provider environment."

In its most recent market share and forecast report, "Next Generation Voice Products," which includes market data for the fourth quarter and full year 2001, Infonetics Research reported that Sonus increased its lead in convergence switch revenues for the fourth quarter and also captured the number one position in port shipments. Sonus also held a commanding lead in revenues for the voice over packet (VoP) market segment for the year. The report highlighted service provider customers that Sonus signed in Q4, including Alestra and Touch America, as well as the strides the company has made in international markets, particularly Asia.

"In Q4 and throughout the year, Sonus continued to increase its market share as other players stumbled, and they clearly have the time-to-market and Tier 1 customer advantage over most next-gen voice vendors," said Kevin Mitchell, directing analyst, Service Provider Networks, Infonetics. "In the voice market overall, we continue to see a shift in service provider capital expenditures from legacy TDM equipment to next-gen voice products, and we believe that Sonus is well-positioned to reap the benefits of this transition."

Synergy Research Group's quarterly report on worldwide VoIP equipment market share named Sonus as the leader in eight market segments. Sonus expanded its share to garner top rankings for overall service provider VoIP infrastructure revenues and port shipments; VoIP gateway revenues and port shipments (all densities); high-density VoIP gateway revenues and port shipments; and combined high-density VoIP/data media gateway revenues and port shipments.

"In Q4, Sonus gained leadership in two additional VoIP market segments, demonstrating the company's continued penetration of the service provider market," said Jeremy Duke, founder and principal analyst, Synergy Research Group. "With its corporate and product development strategies, Sonus is a driving force behind the increasing adoption of packet voice technologies among service providers."

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 November 14, 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 and manufacturing and sourcing risks.

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