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Fusion's Advanced Packet Voice Network Highlighted in Recent Aberdeen Report

WESTFORD, Mass., June 3, 2002 - Sonus Networks (Nasdaq: SONS), a leading provider of packet voice infrastructure solutions for the new public network, today announced that its network deployment with Fusion Communications, a leading next-generation Japanese carrier, was recognized by the Aberdeen Group as one of the most important voice over IP (VoIP) deployments of 2001. The Aberdeen Group recently released its findings on Fusion's packet voice network, along with several other network implementations, in a report titled "What Works: Significant Voice over IP Deployments of 2001." The report examines and evaluates the overall market dynamics and the success factors behind VoIP deployments such as the Fusion network.

"Sonus' work with Fusion, as well as the other case studies in this report, proves VoIP is a business-ready financial, and technical, proposition," said George Peabody, vice president of Aberdeen's NextGen Communications practice. "With its next-generation VoIP network, Fusion Communications achieved significant success in a very short period of time. The Fusion network demonstrates that carrier VoIP is ready for prime time and how VoIP gives carriers a competitive edge. As this technology moves deeper into application-level services, carrier revenue opportunities only increase."

Fusion Communications was established in March 2000 with the mission of becoming Japan's first and premier IP-centric telecommunications carrier, providing services to business and residential phone users in Japan. Utilizing advanced packet technologies, Fusion launched its nationwide VoIP network in April 2001, and is Japan's first carrier to support the integrated transmission of voice and data.

Working together with Sonus and its distribution partner, Nissho Electronics, Fusion implemented Sonus' GSX9000 Open Services Switch, the Insignus Softswitch and the Sonus Insight Management System. The Sonus infrastructure is deployed in 18 cities throughout Japan and is managed from an advanced network operations center (NOC) in Tokyo.

With their Sonus-based network, Fusion serves a mix of residential and enterprise customers, and supports services including long distance, international dialing and PBX access. Using this next-generation platform, Fusion plans to deliver enhanced services such as virtual call centers, as well as providing services to SIP telephones.

A major test of the network came on January 1, 2002, when Fusion offered a New Year's Day promotion providing free calls to existing customers as well as potential subscribers. In response to that promotion, callers drove more than six times the normal daily traffic across the network on that day alone, and the Sonus infrastructure performed flawlessly. The success of the promotion resulted in Fusion attracting new customers to their service, and the Fusion network now supports more than 1.3 million subscriber lines.

"Fusion is viewed as a pioneer in the Japanese telecommunications market, as the first greenfield competitive carrier in Japan and the first to deploy a nationwide VoIP network," said Gary Rogers, vice president, worldwide sales, Sonus Networks. "We are tremendously proud of what Fusion and Sonus have accomplished together, and we look forward to building on our successful partnership."

The full details of Aberdeen's research can be found in "What Works: Significant VoIP Deployments of 2001." For more information on this report, please contact Ian Clause at Aberdeen Group at 800-577-7891 or visit the Aberdeen Group website at www.aberdeen.com.

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 May 10, 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.

GSX9000, Insignus, Sonus Insight and Open Services Architecture are trademarks of Sonus Networks. All other company and product names may be trademarks of the respective companies with which they are associated