Masergy Implementing Full Sonus Packet Voice Solution in Worldwide Network; Service Provider to Offer SIP-Based Voice Services to Enterprise Customers

WESTFORD, Mass., January 22, 2002 – Sonus Networks (Nasdaq: SONS), a leading provider of voice infrastructure solutions for the new public network, today announced that Masergy Communications, Inc., a global provider of customer-controlled network services, is deploying Sonus' packet voice solutions in its intelligent IP/MPLS (Multi-Protocol Label Switching) network. With its Sonus-based network, MASERGY expects to begin delivering revenue-generating voice services to its customers around the world in January 2002.

"Our agreement with Sonus is integral to our business strategy of delivering a comprehensive suite of voice, data and video services to the global enterprise market," said Kenneth Frank, MASERGY's senior vice president of engineering and operations. "Leveraging leading-edge technologies, Sonus' packet solutions form the cornerstone of our voice offering, allowing us to cost-effectively provide a full range of traditional and next-generation telephony services. With Sonus, we are executing on our mission of offering customers fully integrated converged network services."

MASERGY is rolling out a global converged network using Sonus' field-proven Open Services Architecture(TM) (OSA) as the foundation for delivering voice services. MASERGY is deploying all components of the award-winning OSA, including the GSX9000(TM) Open Services Switch and the Insignus^TM Softswitch, as well as the Sonus Insight(TM) Management System, throughout its network infrastructure. MASERGY is also deploying voice applications from Sonus' Platinum OSPASM (Open Services Partner Alliance) member, BroadSoft.

With its Sonus packet voice network, MASERGY will offer business users the traditional voice services they currently enjoy, such as long distance, international and local calling services. Additionally, MASERGY will leverage the advanced IP/MPLS infrastructure to deliver a host of next-generation, SIP (Session Initiation Protocol)-based voice services to enterprise customers.

The MASERGY network fully leverages the capabilities of MPLS to combine the flexibility of IP with the security and traffic management characteristics normally associated with legacy technologies such as frame relay and ATM. This allows companies to run multiple applications at different priorities and different levels of quality of service (QoS), providing unsurpassed service delivery through advanced network programmability and enterprise-wide monitoring and reporting.

"MASERGY truly offers the market a unique value proposition," said Hassan Ahmed, president and CEO, Sonus Networks. "With MASERGY'S innovative network, customers can easily control business applications, such as voice, data and video, while avoiding the costs and complexity of building, maintaining and upgrading the network infrastructure. We are pleased to be working with MASERGY to bring their vision of converged networking to fruition."

MASERGY is deploying Sonus' industry-leading packet voice solutions in major metropolitan areas across the United States. MASERGY IP telephony and data services are available in metropolitan areas across the United States and Europe. MASERGY expects to extend its footprint to include 35 cities in the United States and Europe by the end of 2002.

About Masergy Communications, Inc.

About Masergy Communications, Inc. Founded in 2000, Masergy Communications, Inc., is a privately held Dallas-based global provider of customer-controlled network services for enhanced applications performance. MASERGY specializes in providing companies the control of a private network and the savings of a shared infrastructure to reduce network costs and align business technologies with corporate priorities. For more information about MASERGY, visit the company at www.masergy.com, or call (866) 588-5885.

About Sonus Networks

Sonus Networks, Inc., is a leading provider of packet voice infrastructure products for the new public network. 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 Sonus' Quarterly Report on Form 10-Q, dated November 14, 2001, 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 Company's 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.

Open Services Architecture, GSX9000, Insignus and Sonus Insight are trademarks of Sonus Networks. Open Services Partner Alliance is a service mark of Sonus Networks. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners.