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New Sonus Capabilities Enable Carriers to Securely Interconnect Between IP Networks; Sonus Solution Surpasses Functionality Delivered by Session Border Controllers

WESTFORD, Mass., December 15, 2003 – Sonus Networks (Nasdaq: SONS) today announced that it is delivering new capabilities through its Open Services Architecture (OSA) and voice infrastructure solutions to facilitate the development of the ubiquitous all-IP network. With the recently issued Release 5.1 of its industry-leading GSX9000 Open Services Switch and Insignus Softswitch, Sonus provides major new features and functionality that extend the applications of its solutions and create a new category of product: Network Border Switching.

"Carriers have been deploying packet technologies as the foundation of their voice networks for some time now, enabling them to reduce the cost of their infrastructure and deliver new services," said Mike Hluchyj, Sonus' founder and chief technology officer. "At this stage of the market, we see many 'islands of IP,' and carriers are now ready to take the next step in the evolution of their networks by securely connecting to other carriers, enterprises and even to end users in native IP. The new network border switching capabilities Sonus is introducing today build upon our robust, field-proven solution to address emerging carrier requirements for security, session control and address translation between IP networks."

As packet voice networks continue to proliferate, service providers are moving to connect to others using IP, rather than circuits. This trend opens up new opportunities for carriers in a number of key areas:

• Peering– Carriers can interconnect or "peer" with one another using VoIP, which enables capital and operational efficiencies by eliminating the need to convert between VoIP and circuit voice.
• Enterprise access – Service providers are increasingly using IP as the interface of choice to enterprise customers. Because those customers now expect a bundle that includes both voice and IP data, using IP for transport offers cost and operational benefits. With a direct packet-to-packet interface, enterprise voice services can be converted to VoIP using an enterprise gateway, or may be provided directly as VoIP from the PBX.
• End user access – Communications providers may want to connect end users to the carrier voice service through IP. In this scenario, the customer device can be one of several options, such as an IP phone, a "soft" phone, or a standard telephone attached to an adapter or Integrated Access Device (IAD).
• Application Service Provider (ASP) access – As they continue to deploy VoIP technologies, carriers are eschewing complex SS7-based protocols in favor of IP as the interface to enhanced services application platforms. This offers increased opportunity for implementation of enhanced services by ASPs, who use the IP interface to interact with carrier systems.

These new business opportunities introduce a set of new challenges for service providers, specifically in the areas of security, network availability, address translation and interoperability. While products such as NAT devices, firewalls and session border controllers have been used to solve pieces of the overall problem, until now, there has been no single solution that addresses all of these issues.

The combination of Sonus' GSX9000 Open Services Switch and Insignus Softswitch eliminates the need for multiple partial solutions by providing basic network border switch functionality, including: 

• Network Address Translation (NAT) and topology hiding
• Access control via pinhole firewall
• Denial of Service (DoS) protection
• Bandwidth and Quality of Service (QoS) theft protection
• Signaling-based admission control (SIP or H.323)
• SIP and H.323 Proxy, back-to-back and interworking functions

More importantly, with its network border switching capabilities, Sonus goes beyond the baseline functionality to deliver the advanced features required of a carrier-grade solution:

• Sophisticated control – Sonus' network border switch leverages the robust features of the Insignus Softswitch to enable carriers to control firewall pinholes and routing with options not only based on IP addresses, but using call-related information such as calling subscriber, called subscriber, applicable calling plan and others.
• Media inter-working – Sonus' solution is able to resolve the media incompatibilities that can arise in interconnecting IP devices, such as different codecs, different voice packet sizes and protocol incompatibilities (raw fax vs. T.38, DTMF vs. RFC2833).
• Services on packet-to-packet calls – Sonus' solution provides the same types of standard services on VoIP calls as carriers currently provide on circuit-based calls, allowing carriers to apply tones, announcements and prompts as necessary.
• Support of SIP-T – Sonus supports Session Initiation Protocol for Telephones (SIP-T), which carriers typically use when peering with another carrier via IP, allowing end-to-end call signaling via embedded ISUP information. Sonus also supports dozens of different ISUP variants, which will enable carriers to inter-work between incompatible ISUP variants within SIP-T.
• True carrier-grade implementation – Sonus' network border switch solution has been designed to meet typical carrier requirements, including:
  • At least 99.999% availabilityc
  • Ability to scale to handle large numbers of sessions
  • Traffic controls to handle congestion
  • Complete billing in carrier format
  • Management and troubleshooting of packet voice calls
  • Full Lawful Intercept (e.g. J-STD-025)

"With its new network border switching capabilities, Sonus is ahead of the curve among softswitch and media gateway makers in providing carriers with an integrated approach to addressing the challenges they face in interconnecting their VoIP networks with other carriers and users," said Joe McGarvey, senior analyst, Current Analysis. "The addition of these capabilities is a natural and timely enhancement to Sonus' packet voice platform, one that will benefit carriers as they move forward in the next phase of the VoIP market."  

About Sonus Networks

Sonus Networks, Inc., is a leading provider of packet voice infrastructure solutions for wireline and wireless service providers. With its Open Services Architecture (OSA), Sonus delivers end-to-end solutions addressing a full range of carrier applications, including trunking, residential access and Centrex, tandem switching, and IP voice termination, as well as enhanced services. Sonus' award-winning 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 Westford, Massachusetts. Additional information on Sonus is available at http://www.sonusnet.com.

This release may contain projections or other forward-looking statements regarding future events or the future financial performance of Sonus 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 "Cautionary Statements" section of Sonus' Quarterly Report on Form 10-Q, dated November 10, 2003 and filed with the SEC, which identifies important risk factors that could cause actual results to differ from those contained in the forward-looking statements. These risk factors include, among others, the adverse effect of recent developments in the telecommunications industry, the weakened financial position of many service providers, Sonus' ability to grow its customer base, dependence on new product offerings, market acceptance of its products, rapid technological and market change and manufacturing and sourcing risks. 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.

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.