Leading Vendor of IMS-Ready Architecture Delivers Standards-based Approach to Wireline and Wireless Mobility

CHELMSFORD, Mass. and BARCELONA, Spain, February 13, 2006 - Today at the 3GSM World Congress 2006, Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, unveiled its standards-based solution for enabling subscriber roaming between wireline and wireless environments (Fixed-Mobile Convergence or FMC). The Sonus FMC solution is the latest application for Sonus' award winning IMS architecture, and allows network operators globally to deliver a seamless, consistent and portable experience for end users.

Taking advantage of the penetration of wireless local area networks (WLANs), Sonus' FMC solution allows network operators to provide secure and personalized mobile broadband services, including voice, video, data and other multimedia services over a converged network that leverages the advantages of both mobile networks and WLAN hotspots.

“The introduction of FMC technology changes the entire telecommunications paradigm,” said Hassan Ahmed, chairman and CEO, Sonus Networks. “Network operators are now able to break down the boundaries between wireless and wireline services, capitalizing on the best of both worlds to deliver innovative, high quality applications. The next-generation of users is more mobile than ever before and the ability to deliver innovative services seamlessly and cost-effectively is critical for customer retention and revenue generation. The primary benefit of an IMS architecture is the ability to deliver a unique user experience anywhere and anytime.”

The Sonus FMC solution is based on the emerging standard protocols as defined by the 3rd Generation Partnership Project (3GPP) and includes a combination of its industry leading IMS-ready architecture and elements from its industry-leading partner program, the Open Services Partner Alliance (OSPA). The Sonus FMC solution will support the delivery of advanced voice and data applications, which will allow operators to offer services to enterprises across wireline or wireless, narrowband, wideband or broadband, business or personal network connections. The Sonus FMC solution will be interoperable with second-generation (2G) and third-generation (3G) mobile networks and enable a smooth migration to IMS compliance and an all-IP architecture.

“Sonus has always been an advocate of a standards-based approach to telecom services. Proprietary solutions, particularly when it comes to handset compatibility, fundamentally limit widespread potential,” said Mike Hluchyj, Founder and CTO, Sonus Networks. “Now that the 3GPP has created a basic set of guidelines for FMC, we're eager to help network operators capitalize on the benefits that a converged network can bring. The Sonus IMS architecture provides fixed and mobile operators with a proven solution for delivering a wide range of new applications leveraging the capabilities of FMC.”

“Mobile networks are evolving rapidly, and to keep pace with new demands, network operators globally are moving to VoIP architectures to deliver unique end user experiences,” said Philip Marshall, Vice President of Wireless/Mobile Technologies with Yankee Group. “Vendors like Sonus are shaping the future of the telecommunication industry through its continuous technology leadership and are now enabling wireless operators to migrate their networks aggressively to VoIP and IMS.”

Sonus' award-winning IMS-ready solution, which has been deployed by large-scale wireless and wireline carriers, ISPs, cable MSOs and alternative service providers around the world, allows customers to seamlessly and cost effectively comply with the developing IMS standards and to maximize their investment by delivering converged multimedia services over their existing Sonus architecture.

The Sonus booth will feature an overview of the Sonus IMS architecture and Sonus FMC solution. Sonus' FMC solution will be commercially available in the second half of 2006.

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 15, 2005, and the “Cautionary Statements” section of Sonus' Quarterly Report on Form 10-Q, dated November 8, 2005, 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.

The information in this press release is for informational purposes only and is subject to change at Sonus' sole discretion without notice. Sonus has no obligation or commitment to develop or deliver any future release, upgrade, feature, enhancement or function described in this release. The information is provided “AS IS,” with all faults, and without any warranties whatsoever, express or implied, including, but not limited to, warranties of merchantability, performance, or fitness for a particular purpose.

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.