<PAGE>

                                                                    Exhibit 99.1

               Clarent Corporation Acquires PEAK Software Solutions, Inc.

           REDWOOD CITY, California, July 25, 2000. Clarent Coporation (Nasdaq:
           CLRN), a worldwide leader in providing carrier-grade, phone-to-phone
           Internet Protocol (IP) telephony solutions, today announced that it
           has acquired privately-held PEAK Software Solutions, Inc. of
           Littleton, Colorado. PEAK is a leading communications software
           development and consulting firm specializing in building IP-based,
           carrier class data and telecommunications infrastructure software.

           This acquisition is intended to immediately enhance Clarent's
           intelligent IP telephony and communications software development
           activities by adding 56 highly experienced communications software
           engineers to its R&D team. Leveraging PEAK's expertise in developing
           carrier class software solutions, Clarent expects the acquisition to
           enhance the company's time to market advantage for its core software
           products. The PEAK employees will report to PEAK President Steve
           Langion, who will join Clarent's engineering management team led by
           Senior Vice President and CTO Mike Vargo.

           Mike Vargo commented on the acquisition: "We are extremely pleased to
           be adding the expertise and skills of the PEAK Software Solutions
           team to the Clarent family. We believe that this acquisition should
           enable Clarent to accelerate delivery of products that leverage our
           intelligent, software-driven product architecture and enhance our
           ability to grow our leadership position in the burgeoning IP
           communications marketplace. These products are expected to enable our
           customers and partners to build robust networks designed to deliver
           the services and applications that end customers require."

           "PEAK is very excited to join Clarent and to establish a Clarent
           Research and Development Center in Colorado," said Steve Langion, CEO
           and President, PEAK Software Solutions. "There is important synergy
           between Clarent's vision, its market position and PEAK's software
           development expertise. We look forward to applying our development
           capabilities towards the execution of Clarent's vision and to
           accelerating the introduction of Clarent products into the IP
           telephony marketplace."

           Under the terms of the agreement, Clarent common stock and cash with
           an aggregate value of approximately $60 million have been exchanged
           for all outstanding shares of PEAK. This acquisition is being
           accounted for using purchase accounting and was completed on July 24,
           2000. The acquisition was approved by the board of directors of each
           company.

           Forward Looking Language
           This news release contains forward-looking statements that involve
           risks and

                                       1.
<PAGE>

           uncertainties that could cause actual results or outcomes to differ
           materially from those contemplated by the forward-looking statements.
           Factors that could cause or contribute to such differences include,
           but are not limited to, risks relating to losses of key personnel or
           inability to introduce new products. In addition, statements in this
           press release relating to the expected benefits of the contemplated
           acquisition are subject to risks relating to the timing and
           successful completion of technology and product development efforts,
           integration of the development activities between the companies,
           unanticipated expenditures, changing relationships with customers,
           suppliers and strategic partners and other factors described in the
           most recent periodic reports filed by Clarent with the SEC.

           About Clarent Corporation
           Clarent Corporation (NADAQ: CLRN) is the world leader* in providing
           intelligent, software-driven products for new generation, IP-based
           communications networks. Clarent solutions enable interconnection
           among communications service providers' disparate networks and foster
           the creation of global footprints for more than 260 telecom service
           providers worldwide, including AT&T, NTT, Concert and China Telecom.
           Clarent's software platform encourages innovation by allowing
           carriers to develop limitless new features for consumers and
           enterprises. Founded in 1996, Clarent is headquartered in Redwood
           City, Calif. and has offices in Asia, Europe, Latin America and North
           America. To learn more about Clarent, visit its Web site at
           www.clarent.com.

           About PEAK Software Solutions
           PEAK was founded in 1997 to develop telecommunications and data
           communications products on a contract, project basis for service
           providers and infrastructure vendors. The company is comprised of top
           quality managers, engineers, architects and programmers with hundreds
           of years of combined experience from companies such as AT&T Bell
           Laboratories (BellLabs), Bell Communications Research (BellCore),
           Bell Northern Research (BNR), SUN Microsystems, and Motorola. PEAK's
           current client base consists of major data and telecommunications
           infrastructure vendors and service providers. www.peakss.com

                                       2.