Sonus Networks Supports Mobile Operators' Long Term Evolution Migration Strategy

Sonus Joins VoLGA Forum With Sonus MobilEvolution Architecture To Provide Seamless Migration To LTE

WESTFORD, Mass., March 31, 2009 – Sonus Networks, (Nasdaq: SONS), providing network transformation through IP communications technology, today announced that they are the latest member to join the VoLGA Forum (Voice over LTE Generic Access) and has developed a strategy for supporting mobile operators in the migration to Long Term Evolution (LTE). The overall architecture, known as Sonus MobilEvolution, combines Sonus IP-Voice and Multimedia SIP core network technology with the Sonus MobilEdge wireless access node for IP-based radio access. This enables the delivery of basic voice and SMS services from the circuit core even when using the all IP LTE radio access network, and will allow operators to build a richer communications experience to end-users through voice and multimedia.

Sonus MobilEvolution architecture supports joint interworking of packet and circuit-switched network elements, enabling mobile network operators to initially combine a circuit-switched core network for legacy services with an IP-based access and core network for multimedia services. The Sonus MobilEdge can be used as a VANC (VoLGA Access Network Controller) as defined through the VoLGA forum. The VoLGA forum has been set up to facilitate the delivery of voice and SMS services within the LTE environment from initial development.

"Long-Term Evolution (LTE) is gaining momentum as operators are looking to use LTE as a means of providing fixed broadband services to rural markets and in some cases, to offer fixed broadband outside of their operating territory. LTE has the advantage of essentially unifying mobile technologies into a single standard that has global reach, allowing for greater flexibility, stronger ecosystem, cost reductions and competitiveness. However, delivering existing voice and SMS services for users in this environment is a key challenge that needs to be addressed, so mobile operators can maintain valued services and avoid becoming simple bit pipe providers." commented Teresa Mastrangelo, analyst at Broadbandtrends.com.

"With 12 years of experience in transforming networks to realize the benefits of IP, Sonus is now taking the next step to help mobile operators to migrate seamlessly and rapidly to LTE," commented Shailin Sehgal, vice president, marketing and product management at Sonus Networks. "Users will benefit from a rich communication suite of services, adding presence, IM, chat, video and content transfer to the basic voice communications experience."

About VoLGA

The VoLGA Forum was initiated to specify and promote an approach for extending traditional GSM and UMTS circuit-switched services over LTE access networks.

Based on the existing 3GPP Generic Access Network (GAN) standard, VoLGA technology will enable mobile subscribers to receive a consistent set of voice, SMS (and other circuit-switched) services as they transition between GSM, UMTS and LTE access networks. For mobile operators, VoLGA represents a low-cost, low-risk approach for bringing their primary revenue generating services (voice and SMS) to their upcoming LTE access network deployments.

To promote the widespread adoption of VoLGA technology, VoLGA Forum participants are currently developing a set of open specifications and may be used by vendors and operators of wireless communications systems and applications to develop and deploy interoperable solutions. www.volga-forum.com

About Sonus Networks

Sonus Networks Inc., providing network transformation through IP communications technology, is leading the evolution of communications networks to support the multi-media, multi-device demands of today’s digital lifestyle. Sonus solutions and services enable fixed, mobile and cable operators to gain network awareness and new multi-media capabilities essential to retaining and expanding their subscriber base. Through standards based interoperable solutions and services, Sonus extends the investments made in traditional networks by enabling operators to seamlessly migrate to next generation technology and deliver the secure, reliable, scalable and cost-effective network needed to grow their business. For more information visit 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. For a discussion of the risks and uncertainties which could cause actual results to differ from those contained in the forward-looking statements, see “Risk Factors” in our Annual Report on Form 10-K for the fiscal year ended December 31, 2008. Risk factors include among others: the unpredictability of our quarterly financial results; risks and uncertainties associated with the Company's previous 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 the impact the current global financial market conditions may have on the telecommunications industry. 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.

For more information, please contact:

US Media Contact:
Lucy Millington
1-978-614-8240
lmillington@sonusnet.com

EMEA Media Contact:
Lauren Bishop/Lucia Barbato
+44 (0) 20 7107 2479/2480
sonus.team@catalysis.co.uk