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Leading Research Firms Cahners In-Stat, Infonetics and Synergy Research Group Rank Sonus #1 for Fourth Consecutive Quarter

WESTFORD, Mass., September 5, 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 second quarter of 2001, its fourth consecutive quarter in this position. Reports issued 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.

"The findings from Cahners, Infonetics and Synergy continue to reflect our strong momentum in the market and the growing demand for our packet voice solutions by carriers," said Terri Griffin, vice president, marketing, Sonus Networks. "We are very proud of our leading industry position and the recognition we have received by these highly respected research firms for that achievement. Paying close attention to customer needs and aggressively executing on our product development and sales strategies continue to drive our success."  

Data from Cahners In-Stat Group's quarterly market share report identified Sonus as the continued 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. The results from the second quarter report revealed Sonus' market growth over the previous quarter and confirmed its expanding lead over competitors in these categories.  

"Sonus continues to outperform competitors and expand its market lead for delivering carrier-class VoIP gateways," said Norm Bogen, director, WAN Infrastructure and Services, Cahners In-Stat Group. "Competitive players have not been able to match Sonus' performance in terms of ports or revenues, demonstrating carriers' confidence in Sonus solutions as a means to reduce costs and expand services during the current industry slump."  

Infonetics Research's worldwide market share and forecast service reported that Sonus captured two-thirds of next generation voice/data switch revenues in the second quarter, maintaining Sonus' status as the market leader in this segment. Highlighting Sonus' increased traction with customers, the results of the report illustrated Sonus' growing market share over the previous quarter in contrast to competitors' shares, which declined or remained flat.    

"Sonus has built a solid lead in the next generation voice/data switching segment and gained considerable ground during the last quarter with adoption of their solutions by leading carriers," said Infonetics research analyst Kevin Mitchell. "With service providers deploying next-gen voice products in order to competitively differentiate their offerings and reduce operational costs, it is significant to note that 8 out of 32 the Tier 1 service providers in the US and Canada have chosen to implement Sonus' solutions. This customer base has helped Sonus retain their revenue leading position for the fourth straight quarter in the voice/data switch market."   

Sonus' market leadership was also recognized by Synergy Research Group's quarterly report on VoIP equipment market share. In the report, Sonus received top rankings in several market segments including: service provider VoIP gateway revenues and port shipments; high density VoIP gateway revenues and port shipments; and combined high density VoIP/data media gateway revenues.  

"With its first to market advantage, pedigree customer list, and increasing acceptance of packet-voice technology, Sonus is in a sustainable leadership position as exemplified in its consistent market share gains quarter after quarter," said Jeremy Duke, founder and principal analyst, Synergy Research Group.

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' Quarterly Report on Form 10-Q, dated August 13, 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.

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.