For more information, please contact:

Sonus Named Market Share Leader for Fifth Consecutive Quarter By Cahners In-Stat Group, Infonetics Research and Synergy Research Group

WESTFORD, Mass., December 3, 2001 – Sonus Networks (Nasdaq: SONS) today announced that it has been ranked the worldwide market share leader in carrier-class packet voice switching equipment for a fifth consecutive quarter. Respected industry research firms Cahners In-Stat Group, Infonetics Research and Synergy Research Group all confirmed Sonus' continuing leadership position in a number of market segments during the third quarter of 2001. 

"Leading carriers are increasingly turning to Sonus for their next-generation voice solutions and we are excited that this momentum has been validated yet again by the findings from Cahners, Infonetics and Synergy," said Terri Griffin, vice president, marketing, Sonus Networks. "We are committed to providing the highest levels of technological innovation and customer service to drive carrier satisfaction with our solutions, and in turn, to continue to broaden our market leadership."

In its quarterly market share report, Cahners In-Stat Group 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 data in the third quarter report demonstrated Sonus' steady lead over competitors in these categories. 

"Sonus' positive results continue to outpace the competition, making it the clear leader for delivering carrier-class VoIP gateways," said Norm Bogen, director, WAN Infrastructure and Services, Cahners In-Stat Group. "Carrier confidence in the company continues to be high with an increasing number of customers implementing Sonus solutions to address their next-generation voice services needs."

Confirming Sonus' status as the market leader, Infonetics Research named Sonus number one in next generation voice/data switch revenues for the third quarter in its quarterly worldwide market share and forecast service. The report highlighted service provider customers that Sonus signed in Q3, including BellSouth, Exario Networks and Level 3 Communications.

"With continued adoption of its packet voice solutions by top carriers, Sonus has maintained its revenue leading position for the fifth straight quarter in the voice/data switch market," said Infonetics research analyst Kevin Mitchell. "Overall, we are bullish on the growth of the next-generation voice product market, and Sonus continues to execute in this nascent market, as demonstrated by its expanding customer base." 

Sonus' market leadership was also recognized by Synergy Research Group's quarterly report on VoIP equipment market share. 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. 

"Sonus continues to gain traction in the market and is well positioned to capitalize on the expected increase in packet-voice technology adoption rates," said Jeremy Duke, founder and principal analyst, Synergy Research Group. "In Q3, Sonus still remained the only vendor with a next-generation, high-density VoIP solution that is being deployed in live networks, and is generating revenue." 

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 (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, integration risks relative to its acquisition of telecom technologies, rapid technological and market change and manufacturing and sourcing risks.

Open Services Architecture is a trademark of Sonus Networks. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners.