Company Drives Adoption of Standards-Based NP Solutions for Operators in Eastern Europe, Latin America, South America and Asia-Pacific

WESTFORD, Mass., and PRAGUE, Czech Republic, September 18, 2007 – Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider IP-voice infrastructure solutions, announced today at the Number Portability 2007 Conference in Prague, Czech Republic, that it is helping network operators worldwide streamline regulatory compliance with its new standards-based Electronic Number Mapping (ENUM) enhancement for Number Portability (NP).

"Both fixed and mobile number portability are still relatively new technologies in many parts of the world, including parts of Latin America, South America, Eastern Europe and Asia-Pacific, but regulatory mandates are becoming more and more commonplace," said Chris Drake, vice president, trunking solutions, Sonus Networks. "Sonus is helping network operators in these regions answer demand for cost-effective solutions to the Number Portability challenge by employing a standards-based next generation approach, enabling network operators to focus their network investments on IP and IMS technologies as they achieve regulatory compliance."

In its latest release of its award-winning IP Multimedia Subsystem (IMS)-based platform, Sonus has added standardized ENUM support for NP, as defined by the Internet Engineering Task Force (IETF), that allows network operators to avoid traditional SS7-based switching and the costs associated with it by leveraging next generation technologies. ENUM allows telephone numbers to be routed through IP-based architectures such as IMS using a Domain Name System (DNS)-based architecture, which can facilitate interoperability for a wide range of applications including IP-voice, video, presence, and instant messaging.

Sonus' complete Local and Mobile Number Portability solutions, which are currently deployed in North America, Europe and Japan, support a variety of number portability routing methods, including traditional SS7 TCAP/INAP (Transactional Capabilities Application Part/Intelligent Network Application Part), ENUM, or access to a local number portability routing database. Sonus' number portability solutions are compatible with other vendor equipment, which provides network operators with the ability to leverage one solution to manage their entire network, both legacy and IP-based. By eliminating the need for legacy SS7 Service Control Points and related signaling interfaces, Sonus solutions can significantly reduce operational costs associated with number portability implementations. For additional technical information and specifications, please visit the Sonus website at http://www.sonusnet.com/contents/brochures/Sonus_NPSolutions_DS.pdf.

Sonus is participating this week at Number Portability 2007 in the Czech Republic. The Conference, now in its 12th year, is focused on helping network operators implement Number Portability solutions, share best practice experiences, or refine existing systems. The event includes speakers from leading network operators and regulators from around the world.

About Sonus Networks

Sonus Networks, Inc. is a leading provider of IP-voice infrastructure solutions for wireline and wireless service providers. With its comprehensive IP Multimedia Subsystem (IMS) solution, Sonus addresses the full range of carrier applications, including residential and business voice services, wireless voice and multimedia, trunking and tandem switching, carrier interconnection and enhanced services. Sonus' voice infrastructure solutions are deployed in service provider networks worldwide. Founded in 1997, Sonus is headquartered in Westford, Massachusetts. Additional information on Sonus is available at http://www.sonusnet.com.

This release may contain forward-looking statements regarding future events 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 Item 1A "Risk Factors" of Sonus' Quarterly Report on Form 10-Q for the period ended June 30, 2007, filed with the SEC, which identifies important risk factors that could cause actual results to differ from those contained in the forward-looking statements. Risk factors include among others: the impact of material weaknesses in our disclosure controls and procedures and our internal control over financial reporting on our ability to report our financial results timely and accurately; the unpredictability of our quarterly financial results; risks and uncertainties associated with the Company's restatement of its historical stock option granting practices and accounting including regulatory actions or litigation; risks associated with our international expansion and growth; consolidation in the telecommunications industry; and potential costs resulting from pending securities litigation against the Company. 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, Inc. All other company and product names may be trademarks of the respective companies with which they are associated.