Sonus Extends GSX Family with New GSX4000 Switch; New Hardware Enables Cost-Effective Expansion of VoIP Networks into Untapped Markets.

CHELMSFORD, Mass. & CHICAGO -- Today at SUPERCOMM 2005, Sonus Networks (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, unveiled the GSX4000(TM) Open Services Switch, the industry's first innovative, compact VoIP switch that is designed to deliver carrier-class functionality, reliability and manageability. The GSX4000 was developed specifically for service providers enabling them to expand the reach of their core VoIP networks into new applications, new geographic regions or to deploy IP-based multimedia services. Based on the award-winning GSX9000(TM), the GSX4000 allows service providers to cost-effectively extend the reach of their network boundaries with the same carrier-class functionality that is the hallmark of Sonus' products.

"We have architected our solution from inception to deliver the highest levels of performance, scalability, reliability and interoperability. With the addition of the GSX4000 to Sonus' product family, Sonus now has a complete range of carrier-class VoIP switches enabling service providers to cost-effectively migrate to an all-IP network," said Mike Hluchyj, founder and CTO, Sonus Networks. "The GSX4000 is an ideal solution for service providers that are extending the reach of their packet voice network into new market segments, entering new regions of the world, or introducing new business and consumer services."

The GSX4000 allows service providers to realize the benefits of the GSX9000 on a platform that is right-sized for their immediate needs. By delivering the proven reliability of the GSX9000 in a smaller form factor, service providers are able to cost-effectively support a highly distributed subscriber base or create an initial presence in a large market. The GSX family features industry-leading scalability providing a seamless and straightforward expansion path from several hundred ports to several million ports to meet the demand of the worldwide market. The GSX4000 is being introduced with 24 T1/E1 interfaces. Further, by utilizing advanced DSP technology and the mature software deployed extensively in service provider networks for over six years, the GSX4000 is purpose-built for deployments within service providers' networks worldwide.

"The enhancements to the GSX product family demonstrate that Sonus has a clear understanding of service providers' VoIP strategies and are shaping their product roadmap around solutions that will lead the market as it evolves," said Kevin Mitchell, directing analyst at Infonetics Research. "The GSX4000 cost-effectively extends Sonus' reach into new market opportunities without sacrificing on the high availability and functionality that service providers demand."

Key features and benefits of the GSX4000 Open Services Switch:

--Border Management: As the evolution towards all-IP networks continues, the GSX4000 is a key component of Sonus' Architecture. The GSX4000 fulfills the role of border management by enabling the service providers' VoIP networks to interoperate with other VoIP networks, IP access networks, and legacy PSTN networks, all from a single platform, which is a key prerequisite on the path to an all-IP architecture.

--Carrier-Class Reliability: The GSX4000 is NEBS-compliant in a fully redundant configuration that leverages the GSX9000's customer proven 99.999% reliability design. True to carrier-class expectations, the complete redundancy supports live software upgrades, allowing the network to remain available while implementing new functionality and maintaining active calls in the event of a component failure.

--Advanced Media Services: The GSX4000 implements the same field-proven technologies as the GSX9000 to deliver carrier-class quality of service including toll quality voice that is required by voice networks. The platform not only provides high performance support for compressed codecs, but also employs field proven real-time echo canceller and techniques to support robust handling of fax and data modem calls. The platform supports both G.711 fax and T.38 fax sessions, RFC2833 tone relay functions and the playing of script controlled prompts and announcements.

--Robust Signaling Support: The GSX4000 includes support for the interworking of SS7/C7 variants through the SIP and SIP-T protocols. Further, to integrate legacy and packet-based networks, the GSX4000 has robust IMS media gateway control functionality (MGCF) embedded in its processing module. This provides control and signaling functionality to terminate and originate the wide range of protocols that service providers worldwide expect of a carrier-class switch. Circuit protocols include ISDN, Channel Associated Signaling (CAS) and worldwide variants of SS7/C7.

--Robust, easy-to-use management and back-office integration: An entire network of GSX4000s, along with all other components of Sonus' Architecture (GSX9000s, call/session control function, breakout gateway control function, application servers, etc.), can all be managed by Sonus' web-based Insight(TM) management system from a single console.

--Enables rapid deployment of enhanced services: With its Open Services Partner Alliance (OSPA) and its world-class interoperability lab, Sonus has tested and certified interoperability of industry leading consumer-VoIP and business-VoIP application software, media servers, integrated access devices and SIP phones with its entire product portfolio, including the GSX switches. By handling the time-consuming, costly integration and testing of third party applications and network devices, Sonus reduces the risk, cost and time it takes for service providers to deploy multimedia services.

Availability

The GSX4000 scales in 3U (5.25") rack height increments with 24 T1/E1 circuit interfaces and quad Fast Ethernet packet interfaces. It will be generally available in the third quarter of 2005.

About Sonus Networks

Sonus Networks, Inc. is a leading provider of voice over IP (VoIP) infrastructure solutions for wireline and wireless service providers. Sonus delivers end-to-end solutions addressing a full range of carrier applications, including trunking and tandem switching, residential and business access, network border switching and enhanced services. Sonus' voice infrastructure solutions, including media gateways, softswitches and network management systems, are deployed in service provider networks worldwide. Sonus, founded in 1997, 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, 2005,4 and the "Cautionary Statements" section of Sonus' Quarterly Report on Form 10-Q, dated May 9, 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. In addition, 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. Open Services Architecture, GSX9000 and Insignus are trademarks of Sonus Networks. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners.