Sonus IMS SIP Core Network Provides Carrier-Class Reliability to Standards-Based Service Delivery

WESTFORD, Mass., March 13, 2008 – Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider IP-voice infrastructure solutions, today announced the latest release of its IP Multimedia Subsystem (IMS) core architecture, including upgrades to its SRX™ Call Session Control Function and HSX™ Home Subscriber Server. With its latest release, Sonus Networks empowers network operators to deliver advanced multimedia communications applications and services on a standards-based platform built to meet the rigorous scalability, reliability and security needs of today's largest network operators.

"Our goal is to provide network operators with an IMS core network that will support the delivery of enhanced services to any end-user device, based on the user's preference. With today's release, we've taken Sonus' long history of leadership in SIP-based networks to the next step and added additional scalability and reliability components," said Vikram Saksena, chief technology officer, Sonus Networks.

The proliferation of services such as video calling, video conferencing, instant messaging, chat and push-to-talk services have increased the number and variety of SIP sessions within a service provider network. A central intelligence component in the IMS architecture, the SRX serves as an authentication engine that tells the network which services belong on any given session. Sonus' SRX 2.0 is built on the open-source Linux operating system, Service Availability Forum™ based middleware to provide the most scaleable and future-proof platform available. With today's release, Sonus' IMS core network architecture is compliant with 3GPP Release 7 specifications.

Recognizing that carriers' migration plans to IMS differ, Sonus' IMS core integrates within existing environments, with the ability to scale up as required. The Sonus IMS SIP core has been deployed worldwide and has been the foundation for IMS Forum interoperability testing since the inception of the Forum and its groundbreaking PlugFest events. By enhancing the security and reliability elements, Sonus expands its addressable market and further promotes the adoption of IMS as the foundation for today's most advanced communications networks.

"When migrating to the all IP network, interoperability is key to maximizing immediate revenue opportunities without compromising end-user services and functionality" said Michael Khalilian Chairman & President at the IMS Forum, "Sonus Networks have always been at the forefront of advocating the use of industry standards and forward looking technology to ensure that network providers are able to scale their business effectively."

Interoperability has been performed with the Sonus SRX™ and IMS compliant platforms and user equipment from multiple vendors. As a founder member of the IMS Forum, Sonus is committed to providing reliable technology that will integrate within existing IMS networks.

About Sonus Networks

Sonus Networks, Inc. is a leading provider of IP-voice 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 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-K for the period ended December 31, 2007, 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 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.

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