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WESTFORD, Mass., February 12, 2003 – Sonus Networks (Nasdaq: SONS), a leading provider of packet voice infrastructure solutions for the new public network, today announced that BayPackets' RSI PrepaidTM application has successfully completed interoperability testing with Sonus' InsignusTM Softswitch, becoming the latest product to be "Powered" through the Open Services Partner AllianceSM (OSPA). BayPackets' RSI Prepaid enables service providers to deliver prepaid calling card services to residential and business users in a flexible and cost-effective manner.

"The market for prepaid calling card services has experienced tremendous growth over the past decade, as consumers and corporate users seek ways to control and manage costs," said Michael O'Hara, vice president, marketing, Sonus Networks. "With the RSI Prepaid application, BayPackets delivers a compelling opportunity for carriers to generate new revenues and retain subscribers. Through the interoperability announced today, service providers are assured that they can implement BayPackets prepaid services on their Sonus-based infrastructures."

The BayPackets RSI Prepaid application is built on BayPackets' robust, carrier-grade RSI Network Services Platform, which has been designed to scale to support millions of subscribers and busy hour call attempts (BHCA) in today's carrier networks. BayPackets' open and extensible prepaid solution enables service providers to cost-effectively deploy revenue-generating prepaid services over today's circuit-switched and packet-based networks. The BayPackets RSI Prepaid software also features web-based provisioning and management capabilities to improve operational efficiencies and lower operating expenses.

"Service providers are excited about the incremental revenue potential that prepaid calling card services offer," said Ken Epps, president and CEO, BayPackets. "We are pleased to have completed interoperability testing with our RSI Prepaid and the Sonus product family, and look forward to working with carriers to implement a complete packet-based prepaid solution."

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 to http://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 ArchitectureTM (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 Open Services Architecture is a trademark of Sonus Networks. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners.