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SoftSwitch Achieves More Than 1,600 Calls Per Second in Performance Tests;
Delivers Rich Set of Features, Functionality for Call Management and Service Creation 

WESTFORD, Mass., August 2, 2000 – Sonus Networks (Nasdaq: SONS), a leading provider of voice infrastructure products for the new public network, today revealed results of recent performance tests in which the company’s PSX6000Ô SoftSwitch demonstrated the industry’s highest levels of performance, scalability and reliability.  The performance analysis and validation were conducted by Mier Communications, a leading independent networking consultancy and test center.  In these benchmarks, Sonus’ PSX6000 SoftSwitch achieved 1,650 calls per second, equivalent to 5.94 million BHCA (busy hour call attempts).   Additionally, the PSX6000 proved to be extremely reliable, performing at high processing rates for an extended period of time without dropping a single call.

“We were extremely impressed with the performance and the scalability of the Sonus architecture,” said Mike Hommer, lab testing manager, Mier Communications.  “Sonus’ PSX6000 is a highly reliable system with proven scalability and an impressive call-setup capability.  All of these attributes are critical to carriers building out their next-generation voice infrastructures, and Sonus has demonstrated that it can handle these challenges.”

Mier Communications tested Version 3.0 of the PSX6000 SoftSwitch, conducting tests that included load testing, analysis of the call-setup process itself, as well as tests to verify that call generators used in the testing behaved as they would in actual carrier environments.

Key findings and conclusions of the testing include:

• The PSX6000 SoftSwitch supported up to 1,650 calls per second with a 12-CPU configuration, and 1,400 calls per second with an eight-CPU configuration
• The PSX6000 handled an increasing call load as CPUs were added, from a four-CPU configuration to a 12-CPU setup
• Fail-over from the primary to secondary PSX6000 SoftSwitch occurred in less than one second without dropping a single call

“These test results reflect what we’ve experienced with the PSX6000,” said Allan Van Buhler, vice president of global product development, Global Crossing.  “We needed a solution that would allow us to integrate our three billion minutes of use a month onto our VoIP backbone using just a handful of softswitches.  Combined with their GSX9000 Open Services Switch, the Sonus SoftSwitch delivers the kind of call processing performance and scalability that we require to deploy VoIP as a carrier-class enabling infrastructure.” 

Sonus’ PSX6000 SoftSwitch is an integral component of the company’s Open Services Architecture (OSA), a powerful voice infrastructure platform that enables carriers to deploy packet telephony for trunking, Internet offload and access applications.  Additionally, the OSA provides an open approach through which new services can be created easily and implemented quickly.  The PSX6000 interfaces with third-party feature servers and application servers to deliver revenue-generating enhanced services such as unified communications, single number service, Internet click-to-talk, voice portals and more. 

“As carriers begin deploying next-generation voice networks, their requirements go beyond basic call processing functionality to softswitch solutions that are truly carrier-class, providing the highest levels of performance, redundancy and reliability,” said Mike Hluchyj, founder and chief technology officer, Sonus Networks.  “Our SoftSwitch combines extremely high call processing performance and scalability with a rich feature set, making the PSX6000 the industry’s call management platform of choice.” 

About Mier Communications

Mier Communications, founded in 1988, is an independent networking consultancy and product-test center located in Princeton Junction, NJ. The company pioneered the comparative assessment of networking hardware and software, having developed methodologies for testing products from ATM switches to network operating systems.  In 1995, the company launched its “NetWORKS As Advertised” program, in which any vendor can submit its networking-related products for a comprehensive, independent assessment. MierComms also publishes special reports on important networking technologies. Call 609-275-7311 for more information on the latest report, “Getting VoIP to Work.”  Visit www.mier.com for more information on MierComms’ full line of products and services.

About Sonus Networks

Sonus Networks, Inc. is a leading provider of voice infrastructure products for the new public network.  Sonus’ solutions enable service providers to deploy an integrated network capable of carrying both voice and data traffic, and to deliver a range of innovative, new services.  The Sonus Open Services Architecture (OSA) and award-winning Packet Telephony suite cut the time-to-market for competitive new service products, allowing carriers and third-party developers to expand marketshare and build important new revenue streams.  Its highly scalable products fully interoperate with and extend the life and utility of today’s public network.  Sonus embodies in its management and staff decades of experience in developing carrier-class voice, data and multimedia solutions for implementation in the world’s largest networks.  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 Sonus’ Prospectus dated May 24, 2000, filed with the SEC, which identifies important risk factors that could cause actual results to differ from those contained in the forward-looking statements.  

PSX6000, GSX9000 and Open Services Architecture are trademarks of Sonus Networks.  All other company and product names may be trademarks of the respective companies with which they are associated.