CHELMSFORD, Mass., June 5, 2006 – Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, announced today that Neutral Tandem, Inc., the industry's premier tandem and voice peering company for competitive carriers, has deployed a Sonus solution as the foundation for its next generation network. Neutral Tandem is leveraging Sonus equipment to expand its network into new markets, including Orlando, Boston, and Washington, D.C., while at the same time enhancing existing infrastructure in several key markets including Chicago, New York, Los Angeles, and Miami. By deploying a Sonus-based network infrastructure, Neutral Tandem is improving its core business model by enhancing the cost-efficiency of routing traffic between wireless carriers, cable companies, competitive local exchange carriers (CLECs) and VoIP providers.

Neutral Tandem selected Sonus because of its proven track record for deploying highly scalable, robust, carrier-class networks. On the Sonus platform, Neutral Tandem can expand its current Time-Division Multiplexing (TDM)-to-TDM tandem switching application to include IP termination and IP-to-IP switching services. In addition, as Neutral Tandem continues to expand into new markets, the Sonus platform allows the company to begin rapidly offering service in new cities.

“Neutral Tandem provides a valuable service that offers competitive wireless, wireline, and broadband telephony providers an additional level of redundancy and independence from the incumbent local exchange carrier (ILEC),” said Rian Wren, CEO, Neutral Tandem. “By deploying our patent-pending solutions over a Sonus-based architecture, we can continue to improve the legacy tandem model, which requires competitors to exchange traffic via TDM tandem networks owned by the ILECs.”

“Over the past ten years, traffic patterns have evolved and a greater percentage of traffic is being carried between competitive carriers. Neutral Tandem's solution addresses this distinct market opportunity,” said Hassan Ahmed, chairman and CEO, Sonus Networks. “Neutral Tandem addresses a premier market opportunity, and as demand grows, the Sonus network will deliver value by scaling to meet increased capacity requirements.”

Neutral Tandem has deployed a full suite of Sonus' IMS (IP Multimedia Subsystem)-ready solutions, including the GSX9000™, the PSX™ Policy Server, and the Sonus Insight™ Management System. In addition, Neutral Tandem is deploying the Sonus Network Border Switch for enhanced security and direct IP-to-IP peering capabilities. The Sonus-based network began carrying live traffic in 2005 and is expected to expand into several markets throughout 2006.

About Neutral Tandem

Neutral Tandem, Inc. is the nation's only provider of independent tandem and voice peering services to wireless, wireline, cable and VoIP companies. Founded in 2003, the company has created the largest non-PSTN (Public Switched Telephone Network) tandem network in the U.S., facilitating inter-carrier communications with a cost-effective alternative to the Incumbent Local Exchange Carrier (ILEC) network. Neutral Tandem's solutions build redundancy, security and operational efficiencies into the nation's telecommunications infrastructure by connecting over 100 million end points (terminating numbers) in 40 U.S. markets. The company is headquartered in Chicago. Please visit Neutral Tandem's website at www.neutraltandem.com.

About Sonus Networks

Sonus Networks, Inc. is a leading provider of Voice over IP (VoIP) 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 Chelmsford, 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 the “Risk Factors” section of Sonus' Annual Report on Form 10-K, dated March 14, 2006 and Quarterly Report on Form 10-Q, dated May 8, 2006, both filed with the SEC, which identify 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 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. All other company and product names may be trademarks of the respective companies with which they are associated.