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Sonus Successfully Completes SS7 Testing at BT Exact

WESTFORD, Mass., October 21, 2003 – Sonus Networks (Nasdaq: SONS), a leading provider of carrier packet voice infrastructure solutions, today announced that it has completed rigorous interoperability testing of its products with BT's research, technology and IT operations business, BT Exact. Based on its successful completion of the Signaling System 7 (SS7) testing, Sonus' solution, consisting of the Insignus Softswitch, GSX9000 Open Services Switch and the Sonus Insight Management System, has received the BT Exact "Blue Stamp" of approval. To achieve approval, the product was tested for its conformance to relevant international and UK standards and its ability to work reliably when connected into networks that contain other manufacturers' products.

"We are very proud to have achieved the BT Exact "Blue Stamp" accreditation for our packet voice solutions,' said Michael O'Hara, vice president, marketing, Sonus Networks. "This certification signifies to European carriers that our equipment has been thoroughly tested and ensures them that our systems are suitable for interconnection with BT's UK network. This is an important criteria particularly for service providers deploying multinational infrastructures."

BT Exact's SS7 accreditation tests are designed to validate, to a standard agreed with BT Wholesale, BT's wholesale communications network services and solutions business, that products meet the appropriate ITU-T, ETSI, NICC and PNO-ISC standards that apply to SS7-compatible equipment to be used in the UK. The interworking tests are intended to exercise all aspects of the equipment's expected live behavior, including its ability to handle all call types and respond correctly to maintenance actions, as well as the failure of other equipment in the network. Additionally, BT Exact tests the equipment's performance under conditions such as the receipt of specific message contents or sequences, or failures on the BT switch to which it is connected. Certified products are subject to a final network deployment check to confirm they are correctly installed and configured.

Paul Challener, head of networks and testing portfolio at BT Exact, said: "For Sonus Networks" solutions, the award of "Blue Stamp" accreditation recognizes the successful completion of a wide range of tests selected to demonstrate the switch's ability to operate correctly as a part of the UK PSTN via SS7 IUP signaling. The tests, conducted in our unique UK PSTN reference environment at our Adastral Park headquarters, showed the Sonus solution to operate reliably under all foreseeable network conditions."

About BT Exact

BT Exact is BT's research, technology and IT operations business. It specialises in telecommunications engineering, leading-edge network design, IT system and application development and has extensive expertise in business consulting and human factors. Its knowledge helps its customers across BT Group and in selected other businesses gain maximum advantage from their investments in communications networks and IT systems, develop new capabilities and open new opportunities.

BT Exact brings together the technological expertise of BT's research laboratories and the operational experience of the teams that design and operate BT's IT systems. Backed by a team of over 6,000 technologists, it is active and influential in setting global standards. BT Exact builds on the insights and expertise developed by its research to address the demands of the next-generation internet, as well as advanced data services, information and network security, and software systems to support communications networks worldwide. BT Exact has people based worldwide - including locations across the UK and in Asia, continental Europe, and North America. For more information about BT Exact, please go to http://www.btexact.bt.com/.

About Sonus Networks

Sonus Networks, Inc., is a leading provider of packet voice infrastructure solutions for wireline and wireless service providers. 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 the "Cautionary Statements" section of Sonus' Quarterly Report on Form 10-Q, dated August 13, 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. 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. 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. Insignus and Open Services Architecture are trademarks of Sonus Networks. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners.