Leading Testing and Analysis Firm, CT Labs, Validates Strength of NBS

WESTFORD, Mass., July 16, 2007 – Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider Voice over IP (VoIP) infrastructure solutions, and CT Labs, a full service testing and analysis lab serving converged communications product manufacturers and next-generation network carriers and service providers, announced today that rigorous tests conducted by CT Labs confirmed that Sonus' Network Border Switch provides carrier-class security features that help network operators maintain the integrity of their networks. Unlike traditional peering and security products such as Session Border Controllers (SBCs), Sonus' NBS is a purpose-built IP-based solution that combines session control, PSTN gateway services and security into a single, high performance, carrier-class solution.

"Helping our customers keep their networks up and running seamlessly, even in the face of mounting security threats is one of our most important objectives," said Chris Drake, VP Trunking Solutions, Sonus Networks. "With the Network Border Switch, we're offering our customers one of the most comprehensive security solutions on the market today, and we're pleased that CT Labs validated the strength of our solution through their thorough testing process."

"The Sonus Network Border Switch proved itself in our demanding Empirix Hammer-based tests to be a carrier-class border solution that provided a solid network security layer," said Chris Bajorek, Director, CT Labs. "The NBS has differentiated itself by not only keeping calls active while under attack, but also maintaining the quality of legitimate calls while under attack."

The CT Labs suite of test focused on subjecting the NBS to real-world denial of service attacks. Key findings of the report concluded:

• The Sonus NBS provides an excellent protection boundary under significant adverse attack conditions and Session Initiation Protocol (SIP) call loads at up to 135 calls/sec. Not only did it deliver impressive carrier-grade call completion rates but the NBS was able to maintain high voice quality levels while being subjected to a wide range of aggressive attacks intended to interfere with and prevent SIP services.
• The Sonus NBS successfully rejects gigabit wire rate SIP attacks at carrier class call densities.
• The NBS was found to deliver exceptional call completion and voice quality results as verified by the Empirix Hammer NXT-IP call load generators used in this test.

Full copies of the report, including testing methodologies and detailed results, are available on the Sonus website (www.sonusnetworks.com).

Sonus' NBS solution, which is available on both the GSX9000^™ and GSX4000^™ Open Services Switch platform, gives network operators maximum flexibility in selecting a right-sized solution, allows network operators to leverage the system's sophisticated media handling functionality; extensive IP signaling options that include SIP, SIP-T and H.323; network address and port translation features that protect the privacy of the internal private network topology; session-based firewall functionality; and advanced traffic control features.

About Sonus Networks

Sonus Networks, Inc. is a leading provider of voice over IP (VoIP) 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 dated May 8, 2006, 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 announced review of its historical stock option grants and accounting, including the impact on the Company's financial statements or results, any tax liabilities or penalties, the Company's inability to timely report with the Securities and Exchange Commission, whether the Company will remain listed on the NASDAQ Global Select Market and regulatory actions or litigation arising out of the review or any restatement; 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.

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.

About Empirix

CT Labs is a division of Empirix. Empirix helps organizations adopt complex communications solutions with confidence. We combine the industry's deepest knowledge of voice and self-service applications with our award-winning HAMMER testing and monitoring solutions. Empirix is the only company with expertise that spans the evolution of these advanced technologies across multiple markets – from testing in R&D labs through monitoring the end-user experience. For over a decade, thousands of quality-conscious network equipment manufacturers, service providers and enterprises worldwide have trusted Empirix to reduce the time and cost of integrating new technologies into existing environments. Visit www.empirix.com.

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