Expansion of Interoute's Virtual Voice Network Continues as Voice Traffic Grows 100%

WESTFORD, MA and STAINES, UK, September, 22, 2008 – Sonus Networks, (Nasdaq: SONS), a market leader in IP communications infrastructure, and Interoute, the owner of an advanced next generation voice and data network in Europe, today announced that they are working together to increase the capacity of Interoute's Virtual Voice Network (VVN) in Western Europe, Eastern Europe, the Middle East and the United States.

Interoute has implemented Sonus' IMS compliant technology in over eight European countries and has recently deployed the technology in New York, with further expansion plans underway for 2009. Operators, ISPs and service providers are able to expand their operations and take advantage of a range of SIP services in new markets without making an upfront investment in their own infrastructure.

In addition, Interoute is working to extend the capacity of its VVN platform beyond Europe to the Middle East and other regions, allowing operators, ISPs and service providers to lease network capacity and take advantage of a range of SIP services, permitting them to operate globally without an upfront financial commitment by accessing a ready-made secure, scalable and robust voice network.

This move represents strategic growth in geographic markets for Interoute and demonstrates how Sonus is empowering customers such as Interoute to deliver innovative services at the forefront of emerging markets.

"We are continually investing in state of the art technology and infrastructure in order to develop innovative new services and support the growth of our customers into new markets," commented Gareth Williams, Interoute's CEO. "The Sonus platform continues to perform at a carrier class level and enables us to deliver our core voice business growth plans. We have already seen how the VVN enables operators to enter new markets outside Western Europe; voice traffic across the network grew by over 100 per cent between November 2007 and July 2008 owing to a large increase in demand to and from India, Africa and Asia."

Interoute's VVN provides infrastructure and manages voice traffic for its customers. Interoute offers other benefits to customers interconnecting via Interoute's voice platform such as use of its extensive wholly owned and managed network, end to end testing and the ability for customers to aggregate their traffic on point to multi-point links.

"Sonus has worked with Interoute to deliver and develop its networks since 2002 and our strong relationship and advanced technology continue to support the continued growth of Interoute's voice business," says Tony Morrish, vice president, EMEA for Sonus Networks. "Interoute is a leading innovator in providing this type of Virtual Voice Platform. This latest project expansion is testament to the security, scalability and robust quality of Sonus technology and further demonstrates Sonus' commitment to helping customers in Europe deliver new services and drive growth within and beyond EMEA markets."

Interoute has extended its Sonus IMS compliant network to support new services such as SIP-I peering, adding to the scalability of their existing TDM network with high-density STM-1 interfaces, and expanding the geographical reach of the VVN, supporting new points of presence. The Sonus components implemented include the Sonus InsightTM Element Management System (EMS), Sonus PSXTM Routing Server and Sonus GSX9000TM Media Gateway.

Sonus will be supporting Interoute's ARENA event, taking place in London on 24th September 2008.

About Interoute

Interoute is the owner operator of Europe's most advanced and densely connected voice and data network, encompassing over 56,000 kms of lit fibre. Its full-service next generation network serves more than 12,000 customers across a broad range of sectors from finance to retail and every major European incumbent, as well as the major operators of North America, East and South Asia, governments, universities and research agencies. These organisations find Interoute the ideal partner for hosting content, providing wholesale transit services, corporate access or creating new services. With established operations throughout mainland Europe, North America and Dubai. Interoute also owns and operates dense city networks throughout Europe's major business centres. More than €1 billion in e-commerce transactions flows through its data centres each day, making Interoute a key part of Europe's Digital Supply Chain. www.interoute.com

About Sonus Networks

Sonus Networks, Inc. is a market leader in IP communications infrastructure 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, 2008, 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; actions that may be taken by significant shareholders; risks associated with our international expansion and growth; consolidation in the telecommunications industry; and potential costs resulting from pending securities and patent 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, except as required by law.

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