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Sonus Completes Interop Testing with Insignus Softswitch and Leading Access End Points; Advantage Century Telecommunication, InnoMedia and Integral Access Achieve 'Powered' Status in OSPA

WESTFORD, Mass., December 2, 2002 - Sonus Networks (Nasdaq: SONS), a leading provider of voice infrastructure solutions for the new public network, today announced that it has recently completed a round of tests focusing on interoperability in the access portion of the network.Sonus tested its Insignus^TMSoftswitch with a variety of access devices provided by Sonus Open Services Partner Alliance^SM(OSPA) members Advantage Century Telecommunication, InnoMedia and Integral Access. Based on the successful completion of the rigorous testing, these companies have been designated "Powered" partners in the OSPA program.

"As carriers are now implementing packet voice networks that span from the core of the network to the access edge, the ability to interwork with a range of third-party products, such as LAGs and IADs, becomes even more critical," said Michael O'Hara, vice president, marketing, Sonus Networks."Carriers still desire best-of-breed technologies, but more importantly, they're looking for proven, fully integrated solutions.Together with our OSPA Powered partners, we provide the solutions that give carriers the confidence to roll out end-to-end packet voice networks."

The following products have earned "Powered" status in the OSPA:

• The ACT P103M IP Phonefrom Advantage Century Telecommunication is optimized for current and next-generation networks, supporting a range of protocols and voice codecs, including MGCP, G.711, G.723.1 and G.729AB voice codec with VAD (Voice Activity Detection), CNG (Comfort Noise Generation), and AEC (Acoustic Echo Cancellation) G.168 voice quality control features.The user-friendly ACT P103M IP Phone can be configured via a web browser or directly through the phone menu, and supports features such as speed dialing, call holding, call transfer, call forward and directory services.
• PurePacketfrom Integral Accessis a multi-service access platform that utilizes an IP/MPLS based architecture for guaranteed last-mile QoS, enabling carriers to deliver a comprehensive set of converged and next-generation services.It provides simultaneous support for circuit switch networks and softswitch architectures as a line access gateway.PurePacket includes central office aggregation and customer premise equipment, as well as an object-oriented operations management system.
• The InnoMedia MTA 3328is a standalone broadband VoIP CPE device that offers 4 voice lines with quality of service features that ensure PSTN voice quality, allowing carriers to offer multiple services over the same converged broadband IP network. The MTA 3328 is easy to install, is compatible with standard analog telephone sets, offers fax support and three-way calling, supports CLASS features with call agents or softswitches, and also supports auto-provisioning.

The OSPA's mission is to help empower standards-based interoperability between key enhanced services applications, network infrastructure, and Sonus products.Sonus' OSPA Interoperability Lab is uniquely positioned to test packet voice solutions through the use of state-of-the-art testing equipment within environmentally controlled facilities.Once an OSPA member demonstrates interoperability with a Sonus product, the partner becomes "Powered."Sonus and its "Powered" partners collaborate to deliver end-to-end packet-based network solutions using best-of-breed technologies and applications.

About Sonus' OSPA

Sonus Networks' Open Services Partner Alliance program provides a framework that offers service providers end-to-end packet-based network solutions using best-of-breed technologies and applications.The goal of the OSPA is to empower standards-based interoperability between applications, hardware vendors, and the Sonus product family.An integral part of the Sonus OSPA, the OSPA Interoperability Laboratory is the first in the industry where product interoperability is verified, trial testing is performed and complete solutions are ultimately produced.To find additional information on the OSPA, including a list of all OSPA partners, log on tohttp://ospa.sonusnet.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^TM(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 Partner Alliance is a service mark of Sonus Networks and Insignus 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.