Sonus Teams With NMS Communications To Streamline Delivery Of IMS Applications To Mobile Handsets Over next-Generation Networks

Sonus Networks to Integrate Software Solutions from NMS to Enable Innovative New Services for Mobile Subscribers

Chelmsford, MA and LAS VEGAS, NV, April 5, 2006 – Today at CTIA 2006, Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, and NMS Communications (NASDAQ: NMSS), a leading provider of technologies and solutions for mobile applications and infrastructure, announced that the two companies have entered into a non-exclusive interoperability and co-marketing agreement to streamline the delivery of IP Multimedia Subsystem (IMS)-based applications and services to mobile handsets. By integrating NMS' IMS Mobile Client with Sonus' industry leading IMS-ready architecture, wireless and wireline operators will be able to rapidly deploy a full suite of IMS-based multimedia services including NMS' Active Phone Book and presence-driven applications such as instant messaging, push-to-talk and video sharing on a wide variety of mobile handsets.

"Today's generation of mobile phone users wants more than just voice; they want to leverage a full suite of data and presence-driven tools that bring the communication experience to the next level," said Mike Hluchyj, Founder and Chief Technology Officer, Sonus Networks. "By integrating NMS' client-side technology with the most robust IMS-ready network architecture available on the market today, we're empowering network operators to unleash the potential of IMS and offer consumers a new breed of innovative services and powerful applications."

"From day one, Sonus and NMS have embraced the principles that are the foundation of IMS and have heralded the importance of dynamic new applications as the cornerstone of a successful service offering that is attractive to end users, said John Orlando, chief marketing officer, NMS Communications. This interoperability and co-marketing relationship leverages Sonus' experience in the IMS-industry along with NMS' rich suite of IMS applications to help operators quickly get their services to market, accelerate service take rates and drive annual revenue per user."

Recognized as the global packet voice leader by independent market research firms, Sonus' IMS-ready architecture is deployed in some of the world's largest packet voice networks, which carried approximately 19 billion minutes of IP-based voice traffic in the month of March alone. Sonus' IMS-ready SMARRT" Wireless Solution provides a foundation for migration to full 3G network compliance while delivering value to today's 2G and 2.5G Networks. By enabling interoperability with NMS' IMS Mobile Client network operators can rapidly deploy a growing number of multimedia IP communication services on mobile devices spanning 2.5G, EDGE, 3G IMS, WiFi and Bluetooth wireless networks.

NMS' IMS Mobile Client can be rapidly deployed across a range of mobile phone manufacturers' existing handsets and can be customized and re-branded for use within a service provider's network. The NMS IMS Mobile Client is available today for network equipment and service vendors bringing to market pre-IMS and IMS mobile solutions to wireless and fixed/mobile operators worldwide.

About NMS Communications

NMS Communications (NASDAQ:NMSS) is a leading provider of technologies and solutions for mobile applications and infrastructure. NMS develops products that enable new mobile voice, data and video applications and improve the performance and quality of wireless networks, helping our customers grow their revenues and profits. Visit www.nmscommunications.com for more information.

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, 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. All other company and product names may be trademarks of the respective companies with which they are associated.