Alestra Plans to Decommission Legacy Infrastructure; Deliver State-of-the-Art Services to Subscribers with Sonus-Based Network

WESTFORD, Mass., November 13, 2007 – Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider IP-voice infrastructure solutions, announced today that Alestra, an advanced data and voice telecommunications services operator, majority owned by Mexican leading industrial conglomerate Alfa and 49 percent-owned by AT&T Inc, plans a large-scale expansion of its Sonus-based network. Alestra's Sonus-based next-generation IP-voice network will be the most advanced Voice over IP communications network in Mexico. By leveraging Alestra's own Internet Protocol (IP) and MPLS network, Alestra is able to increase teledensity in the region without installing costly new traditional last-mile telephone connections. In addition, Alestra is partially relying on Sonus Networks as well as other Advanced IP Technology partners to help meet recent regulatory requirements mandating network operators to provide Local Number Portability (LNP) during 2008.

The initial phase of the project allows for Alestra to decommission legacy infrastructure for Local Service in major markets such as: Mexico City, Monterrey, Guadalajara, Tijuana, and Juarez. Sonus' proven ability to deliver end-user services over its IP Multimedia Subsystem (IMS)-based network infrastructure, coupled with its robust solution for efficient LNP implementation and support were critical factors in Alestra's decision. Alestra has been a Sonus customer since 2001, when the company selected Sonus to offload Internet traffic from their circuit switched network. Since the initial deployment, Alestra has continued to leverage its Sonus network in a variety of applications, including H323 and SIP routing, PBX and IP-PBX termination, and carrier peering via TCP/IP. This recent expansion extends Alestra's Sonus footprint into its local access network, improving operating performance and supporting the roll out of business-critical and lifestyle-changing new services. Mexico's policies support the evolution and expansion of its communications infrastructure, and Alestra is leading this new wave of change in the region.

"Mexico is rapidly expanding its position as a leader in the digital revolution. Alestra is working with all relevant players in the industry, government and academia to build the foundations of the communications network of the future. We've witnessed first-hand the benefits a Sonus-based network has delivered in other parts of our network, and we are pleased to be leveraging those advantages at the edge of our network where we can not only achieve regulatory compliance, but also positively impact our customers' experience," said Rolando Zubiran, CEO, Alestra.

"It is rewarding to see one of our earliest customers still actively investing in its Sonus-based network, as it validates the value we bring to customers and our ability to help them address changing market dynamics," said Hassan Ahmed, president, chairman and CEO, Sonus Networks. "With the rollout of this end-to-end IP network, Alestra’s customers can experience first-hand the investments Alestra has made in their cutting-edge IP voice network."

"As a Service Provider our commitment to our customers is to provide them with a high-quality operational experience. This is a reason to rely on experienced and committed infrastructure partners such as Sonus." said Alejandro Irigoyen, VP, COO and CIO, Alestra.

"In the past years, Sonus has continued to innovate, and its platform today provides us with the flexibility we need to help meet emerging regulatory and end-user demands, while allowing us to scale our business effortlessly," Adrian Cuadros, CTO, Alestra.

Alestra is continuing to deploy Sonus' complete IMS-based network infrastructure including the ASX™ Access Server, the GSX9000™ Open Services Switch, the PSX™ Call Routing Server, and the SGX™ SS7 Signaling Gateway. As a key component of the solution, Alestra is leveraging Sonus' recently announced new high density Circuit Network Server (CNS) cards that facilitate the rapid migration of traffic onto the new E1 network, the dominant signaling standard in Latin America. Alestra has also enlisted the help of Sonus' professional services team to support the turnkey integration process. By leveraging Sonus suite of migration tools, Alestra will be able to conduct live migrations without interrupting services to its end users. Alestra's recent migration path to IP is driven in part by recent regulatory mandates requiring network operators to provide Local Number Portability (LNP) solutions to customers. Mexico's telecommunications regulator, Comision Federal de Telecomunicaciones (Cofetel), has called upon the country’s telecommunication providers to offer number portability for both mobile and landline networks. Alestra is capping investment in its legacy infrastructure and is instead opting for a rapid expansion of its next-generation platform with robust support for various NP solutions to meet the current regulations.

"Mexico is dedicated to bringing its population the advanced communication systems of the 21st century. As broadband adoption has continued to increase, Mexico is taking steps to ensure consumers have options in their choice telecommunications providers, and wireless subscribers continue to accelerate," said Stéphane Téral Principal Analyst, Service Provider VoIP, IMS, and FMC with Infonetics Research. "Now is an important time for the emerging markets as they evolve communications networks to match the growth in their economies."

About Alestra

ALESTRA is a leading provider of network solutions, data and value added services to the residential and business customers of all sizes, activities, and scopes in Mexico. ALESTRA is the leader Service Provider for a full spectrum of Managed, VPN, Security, Internet and Converged services in its relevant market. ALESTRA is the first carrier in Mexico to obtain both, the ISO 9002 certification for all its processes, and the ISO 27001 certification for the VPN and Internet services – one of only a few Network Operators in the world-, achieving a strategic position ahead of its competitors. ALESTRA's network, whose optical backbone network is based on high-edge technology, delivers connectivity to 199 cities in Mexico, through a 5,900 km. of fiber optics, providing seamless access to AT&T Worldwide Network, which carries hundreds of millions of data and voice messages in over 280 countries and territories worldwide every day.
http://www.alestra.com.mx

About Sonus Networks

Sonus Networks, Inc. is a leading provider of IP-voice infrastructure solutions for wireline and wireless service providers. With its comprehensive IP Multimedia Subsystem (IMS) solution, Sonus addresses the full range of carrier applications, including residential and business voice services, wireless voice and multimedia, trunking and tandem switching, carrier interconnection and enhanced services. Sonus' voice infrastructure solutions are deployed in service provider networks worldwide. Founded in 1997, Sonus is headquartered in Westford, 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 Item 1A "Risk Factors" of Sonus' Quarterly Report on Form 10-Q for the period ended September 30, 2007, filed with the SEC, which identifies important risk factors that could cause actual results to differ from those contained in the forward-looking statements. Risk factors include among others: the impact of material weaknesses in our disclosure controls and procedures and our internal control over financial reporting on our ability to report our financial results timely and accurately; the unpredictability of our quarterly financial results; risks and uncertainties associated with the Company's restatement of its historical stock option granting practices and accounting including regulatory actions or litigation; risks associated with our international expansion and growth; consolidation in the telecommunications industry; and potential costs resulting from pending securities litigation against the Company. 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, Inc. All other company and product names may be trademarks of the respective companies with which they are associated.