Market Leading Sonus Platform Enables COLT to Reduce Costs and Offer New Services to Subscribers Across Europe

WESTFORD, MA. and STAINES, UK, July 14, 2008 – Sonus Networks, Inc. (Nasdaq: SONS), a market leader in IP communications infrastructure, today announced that it has been selected by COLT to deliver the core IP-voice infrastructure for the next phase of COLT's next-generation network (NGN) deployment. COLT is an award-winning and leading provider of data, voice and managed services to business and governments, serving 100 cities in 13 countries across Europe.

COLT is deploying a complete edge to edge Sonus IP-based session control network with gateways in six major European cities. The solution includes centralized routing, and session border security for IP access and peering. The network is operational in London, Frankfurt and Paris and will extend to Zurich, Milan and Madrid by the end of summer 2008.

"We chose Sonus Networks following a rigorous and extensive testing and review process," said Dr. Alireza Mahmoodshahi, COLT's chief technology officer. "We found that Sonus was the best partner for the session control technology which is robust, scalable and interoperable with our existing networks. We look forward to working with Sonus to support our next generation network rollout."

"Sonus Networks is very pleased to have been chosen by COLT to be part of its next generation network," said Tony Morrish, vice president EMEA of Sonus Networks. "COLT is one of Europe's premier carriers for business subscribers, their decision validates the value Sonus delivers with our integrated solutions for the core network, subscriber services and edge security. By deploying a Sonus-built network in Europe, COLT will be able to offer its customers a range of innovative applications and in addition will be able to dramatically drive down the costs of maintaining its legacy equipment, making its business more resource efficient."

About COLT

COLT is a leading European provider of business communications. COLT specializes in providing data, voice and managed services to major businesses, SMEs and wholesale customers. COLT owns and operates a 13-country, 25,000km network that includes metropolitan area networks in 34 major European cities with direct fiber connections into 15,000 buildings and 18 COLT data centers.

COLT Telecom Group S.A. is listed on the London Stock Exchange (COLT). Information about COLT and its services can be found at www.colt.net.

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 March 31, 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 or litigation; 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.

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.