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Release 5.0 of Sonus' Open Services Architecture Delivers Important Voice VPN Capabilities, International Signaling and Operational Features

WESTFORD, Mass., February 5, 2003 – Sonus Networks (Nasdaq: SONS) today announced the general availability of Release 5.0 of its packet voice infrastructure solutions. The latest version of the Sonus Open Services Architecture (OSA) provides greater value to service providers in three important areas: new revenue-generating opportunities enabled by a comprehensive suite of voice VPN features; expanded international capabilities delivered through a new set of international signaling variants; and network performance optimization enabled through a range of critical traffic controls.

"Sonus' packet voice infrastructure solutions have been deployed for more than four years in service provider networks and now support traffic volumes of 4 billion minutes of use per month," said Michael O'Hara, vice president, marketing, Sonus Networks. "With the fifth version of our Open Services Architecture, we are taking next-generation voice beyond the capabilities of legacy circuit switches, providing even greater value to our customers."

In Release 5.0, Sonus delivers its SMARRT Voice VPN, enabling service providers to offer a complete packet-based voice VPN service to enterprise customers. With the carrier-hosted SMARRT Voice VPN service, enterprises gain the ability to connect multiple, geographically distributed sites and remote users in a single "virtual" network, allowing users to access corporate resources and use features as if they were located in the main office. Deployment of the IP-based SMARRT Voice VPN minimizes carrier infrastructure requirements, significantly reduces capital and operational costs, and speeds time to market. Additionally, SMARRT Voice VPN easily integrates with other enhanced services to create bundled services that enable the carrier to increase brand loyalty and reduce subscriber churn.

"Service providers globally are looking to small to medium business and corporate users as the primary target markets for revenue-generating packet voice services," said Christin Flynn, director, Communications Network Infrastructure, The Yankee Group. "Support for voice VPN is a key component of those new services. Sonus' Release 5.0 incorporates those critical VPN support features as well as the international signaling variants to give service providers the tools they need to win business in any global region."

Sonus is also further expanding its international capabilities with the delivery of new ISUP signaling variants. In the latest version of the Insignus Softswitch, Sonus has added support for national SS7 variants including Argentina, Brazil, Chile, China, India and Spain. With the addition of these new signaling types, Sonus now supports more than 30 SS7 variants and international versions of ISDN PRI and CAS, ensuring that carriers can easily deploy networks that span the globe.

Finally, Sonus is delivering a set of key traffic controls, enabling telecommunications network operations managers to optimize call throughput during periods of congestion and traffic overload, such as holidays or emergency events. Traffic controls offered in Release 5.0 include Code/Call Gapping, which prevents calls to destinations that may be experiencing unusually high levels of traffic due to a disaster or national telephone promotion, for example, and Directional Reservation Equipment (DRE), which enables carriers to reserve a number of trunks for one-way service.

"The significant enhancements delivered in our new software address the important operational requirements of the largest telecommunications service providers in particular," continued O'Hara. "With the advances announced today, we build on the robust features and capabilities that have made Sonus the choice of leading carriers around the world."

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 13, 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 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, SMARRT and Insignus are trademarks of Sonus Networks. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners.