In-Stat/MDR, Infonetics Research and Synergy Research Group Rank Sonus Market Share Leader for Q1 2002

WESTFORD, Mass., May 28, 2002 - Sonus Networks (Nasdaq: SONS) today announced that it has been named worldwide market share leader for carrier-class packet voice equipment, a position the company has held for seven consecutive quarters. Leading industry research firms In-Stat/MDR, Infonetics Research and Synergy Research Group recently issued first quarter 2002 market share reports confirming Sonus' continued leadership position in a number of market segments.

"Carriers recognize the important economic benefits of implementing packet voice solutions and as such, are still keenly focused on migrating to next-gen infrastructures," said Terri Griffin, vice president, marketing, Sonus Networks. "The reports issued by In-Stat/MDR, Infonetics and Synergy underscore our position as a significant player in the telecom industry and as a catalyst in driving the further adoption of packet voice technologies."

The report issued by In-Stat/MDR ranked Sonus number one in a number of categories, including 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.

"In a challenging market for carrier equipment, Sonus continues to lead the packet voice evolution with proven products," said Norm Bogen, director, WAN Infrastructure & Services at In-Stat/MDR.

Infonetics Research recently released its first quarter market share results and forecast, which found that Sonus led the market in providing voice/data switches, in both port shipments and revenues. Infonetics again named Sonus the industry leader in revenues and DS0s shipments of VoP and ICD applications of convergence switches.

"It was a tough quarter for most next-gen voice equipment vendors, yet despite the challenging environment, Sonus remained the market leader in our convergence switch category," said Kevin Mitchell, directing analyst, Service Provider Networks, Infonetics Research. "With 80% share for VoP revenues in the convergence switch market in 1Q02, Sonus continues to command a dominant position among next-generation infrastructure providers."

Sonus was ranked the number one provider for several segments in Synergy Research Group's first quarter report on worldwide VoIP equipment market share. According to the Synergy report, Sonus was the market share leader in overall service provider VoIP infrastructure port shipments; service provider VoIP gateway revenues and port shipments (all densities); and high-density VoIP gateway revenues and port shipments.

"CapEx reductions may have temporarily tamed the momentum of the packet voice market, but we believe the opportunity remains one of the most important in telecom," said Jeremy Duke, founder and principal analyst, Synergy Research Group. "Sonus remains a strategic leader to take full advantage of this transition."

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' 2001 Annual Report on Form 10-K, dated March 27, 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.

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