Interoute Leverages Sonus' IMS Solution to Support Increased Demand for Leading VoIP Services

SWINDON, UK., May 10, 2006 – Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider Voice over IP (VoIP) infrastructure solutions, announced today that Interoute, owner and operator of one of Europe's most advanced telecommunications networks, has selected Sonus Networks' IMS (IP Multimedia Subsystem)-ready network infrastructure solutions to support the multimillion dollar expansion of its IP-based voice network into several major markets, including Madrid, Spain and Milan, Italy. The Sonus solution offers Interoute the authentication and security features necessary to support its carrier-class Virtual Voice Network (VVN) service and Arena, Interoute's commission-free voice exchange, which gives carriers the ability to exchange traffic securely and flexibly with other operators around the world. Sonus' IMS-ready, standards-based platform was selected because it provides Interoute with the scalability and reliability necessary to meet the growing demand for the company's enhanced voice services.

“For years Sonus and Interoute have partnered to develop one of Europe's most sophisticated VoIP networks. Interoute has been a pioneer in the rollout of high value IP-based services, such as iSip and Arena, and continues to invest in its Sonus-based network to differentiate itself as one of the premier providers of VoIP services in the region,” said Hassan Ahmed, chairman and CEO, Sonus Networks. “As Interoute further extends its presence in cities throughout Europe, Sonus is uniquely positioned to help them meet their growth objectives and support the increasing amount of traffic being carried on their network.”

“We selected the Sonus platform because, from day one, we recognized the flexibility that its distributed, standards-based architecture would deliver,” said Matthew Finnie, CTO Interoute. “The Sonus platform utilizes sound engineering principles fundamentally in line with the emerging IMS standards, which enables the development of standards-based services such as enhanced content aggregation and delivery. A standards-based architecture is essential for the shared infrastructure products that Interoute offers to our customers.”

Interoute has been a Sonus customer since 2002 and has deployed the complete Sonus architecture, including the GSX9000™ Open Services Switch, the PSX™ Call Routing Server and the Sonus Insight™ Management System in cities across Europe and North America.

About Interoute

Interoute is Europe's fastest growing telecoms provider and owner operator of the continent's most advanced and densely connected voice and data network. It delivers intelligent, customer-controlled network services to a diverse range of businesses including carriers, mobile operators, service providers, enterprise customers and governments. With established operations throughout mainland Europe and North America, Interoute also owns and operates long-haul and dense city networks throughout Europe's major business centers

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, Inc. Sonus GSX9000 Open Services Switch, PSX Call Routing Server, SGX Signaling Gateway, and the Sonus Insight Management System are trademarks of Sonus Networks, Inc. All other company and product names may be trademarks of the respective companies with which they are associated.