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CHELMSFORD, Mass., June 29, 2004 – Sonus Networks (Nasdaq: SONSE), a leading provider of voice over IP (VoIP) infrastructure solutions, today announced that it has received a formal order of private investigation from the Securities and Exchange Commission. On February 11, 2004, Sonus announced that it had notified the Commission of the Company’s independent investigation following the delay in reporting its fourth quarter and full fiscal year financial results for the year ended December 31, 2003. The matter has been the subject of an informal inquiry by the Commission. Sonus has been fully cooperating with the Commission and will continue to cooperate in this formal investigation.

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 Open Services ArchitectureTM (OSA), Sonus delivers end-to-end solutions addressing a full range of carrier applications, including trunking and tandem switching, residential and business access, network border switching and enhanced services. Sonus’ 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 Chelmsford, 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. Risk factors include, among others, uncertainties regarding the timing of the Company's completion of the audit and filing of its Annual Report on Form 10-K/A for 2003 and future periodic reports, the possibility that Sonus may be delisted from Nasdaq, risks as to the litigation and SEC investigation with respect to the foregoing and related matters, unforeseen issues encountered in the completion of the audit, uncertainties regarding the extent to which prior period financial statements will be restated, the continued adverse effect of developments in the telecommunications industry, Sonus' ability to grow its customer base, dependence on new product offerings, market acceptance of its products, competition from large incumbent vendors, 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, Insignus and Sonus Insight are trademarks of Sonus Networks. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners.