Industry Research Firms Rank Sonus #1 in Carrier VoIP Market for First Quarter 2004

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Chicago, IL, June 22, 2004 – Sonus Networks (Nasdaq:SONSE),today announced that industry research firms Synergy Research Group and In-Stat/MDR recently issued quarterly market share reports naming Sonus as the market share leader in several segments of the carrier voice over IP (VoIP) equipment market.

"There is tremendous excitement in the VoIP industry right now, as incumbent carriers and next-generation service providers alike are making the move to IP voice networks," said Michael O'Hara, vice president, marketing, Sonus Networks. "We are pleased to be recognized as an industry leader by Synergy and In-Stat for the first quarter of 2004. Even more important are the network milestones that we continue to achieve with our customers and the amount of VoIP minutes that we are driving across our customers' networks each month."

Recent market analysis by Synergy Research Group showed that Sonus Networks holds global leadership positions in several market segments. According to Synergy, rankings for Sonus include number one positions in high-density VoIP media gateway port shipments and VoIP media gateway port shipments, all densities.

"Service provider adoption of packet voice continues to accelerate, resulting in significant growth of the carrier packet voice market and an even more dramatic decrease in the traditional Class 4 and Class 5 TDM equipment market in the first quarter," commented Jeremy Duke, founder and principal analyst, Synergy Research Group. "Sonus is a driving force in helping carriers make the transition from circuit to packet, and they continue to hold a leadership position in the VoIP market."

In-Stat/MDR also released its first quarter market share report, which shows Sonus as the leader in high-density voice gateway port shipments.

"A pioneer in the VoIP industry, Sonus Networks continues to deliver best-selling solutions," said Norm Bogen, director, Networking, In-Stat/MDR. "Carrier acceptance of Sonus' products is undeniable, as Sonus has held a leadership position since we began tracking this market four years ago."

The Synergy and In-Stat/MDR reports provide preliminary market share estimates developed by Synergy and In-Stat/MDR respectively.

ABOUT SONUS NETWORKS

Sonus Networks, Inc. is a leading provider of voice over IP (VoIP) infrastructure solutions for wireline and wireless service providers. With its Open Services ArchitectureTM (OSA), Sonus delivers end-to-end solutions addressing a full range of carrier applications, including trunking and tandem switching, residential and business access, network border switching and enhanced services. Sonus’ 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 Chelmsford, 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 the “Cautionary Statements” section of Sonus’ Quarterly Report on Form 10-Q, dated November 10, 2003 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. Risk factors include, among others, uncertainties regarding the timing of the Company’s completion of the audit and filing of its Annual Report on Form 10-K/A for 2003 and future periodic reports, the possibility that Sonus may be delisted from Nasdaq, risks as to the litigation and SEC investigation with respect to the foregoing and related matters, unforeseen issues encountered in the completion of the audit, uncertainties regarding the extent to which prior period financial statements will be restated, the continued adverse effect of developments in the telecommunications industry, Sonus’ ability to grow its customer base, dependence on new product offerings, market acceptance of its products, competition from large incumbent vendors, rapid technological and market change and manufacturing and sourcing risks. In addition, any forward-looking statements represent Sonus’ views only as of today and should not be relied upon as representing Sonus’ views as of any subsequent date. While Sonus may elect to update forward-looking statements at some point, Sonus specifically disclaims any obligation to do so.

Sonus is a registered trademark of Sonus Networks. Open Services Architecture, GSX9000, Insignus and Sonus Insight are trademarks of Sonus Networks. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners.