Avici Systems TSR and Composite Links Deliver Top Performance in Isocore Labs Independent Evaluation; Independent Test Validates Largest Industry Trunk Ever Tested.

CHICAGO -- Avici Systems (NASDAQ: AVCI) today announced that its Composite Links(TM) technology has achieved top performance results in its recent independent and comprehensive verification by Isocore Internetworking Labs, the technology validation leader in next generation IP and optical networking. Isocore tested the Avici TSR(R) and its Composite Links and successfully demonstrated link stability while scaling from 40Gbps to 130Gbps without any service outage while multiple interfaces were added to this bundled link, showing how service providers can dynamically scale without the worry of downtime, service disruption or costly physical provisioning.

Avici's Composite Links gives carriers a powerful tool for simplifying networks and protecting links. By aggregating up to 64 physical links into a single logical link, carriers can seamlessly expand link capacity, improve network utilization and costs, extend the life cycle of existing equipment and provide improved link reliability. With sub-50 ms failover times, traffic is rapidly redistributed from a failed member link without impacting services.

The Isocore test was conducted to simulate the addition of capacity to an existing Composite Link (from 40 Gbps to 130 Gbps), and a variety of administrative actions and system and fiber failures. The test configuration included four Avici TSR routers, with one of the chassis' being a Dual Chassis system, and a Spirent AX/4000 to generate traffic across the system. The Composite Links test survived both administrative and accidental loss of member links with less than 50 ms of interruption per event, which is considered "hitless" as they do not noticeably impact even the most demanding applications such as Voice over IP.

Isocore noted that Avici's Composite Links are designed to support link members with varying capacity, in-service addition and removal of member-links, and rapid identification of failed members, with traffic quickly rerouted along surviving links. Due to the distributed nature of the TSR architecture, members can be distributed among multiple modules across multiples chassis' in the same scalable router without a decrease in reliability, capacity or scalability.

"Avici's Composite Links technology can allow service providers to elegantly provision additional capacity to accommodate higher-bandwidth applications and improve network utilization without service disruption or costly provisioning," said Dr. Bijan Jabbari, president of Isocore. "By distributing the interfaces across several modules in several chassis, and applying the correct signaling procedures, it is possible to provide excellent recovery times in the event of failures."

"Our test with Isocore was the largest trunk ever created in a testing or real-world environment, and validated the uniqueness of our Composite Links technology," said Esmeralda Swartz, vice president of marketing at Avici Systems. "Avici is committed to creating Simple Secure Networks that are not complex and costly to operate and manage, and our Composite Links technology is just one example of how we are achieving this to provide inherent scalability, reliability and flexibility for current and future networks."

To view the report entitled, "Avici Systems TSR Composite Links Scalability Validation," please visit the Avici website at: http://www.avici.com/pdf/AviciCompositeLinksValidationv2a1.pdf.

About Isocore

The goal of Isocore's Internetworking Lab is to advance internetworking through technology validation and product verification and to promote development and rapid deployment of innovative networking technologies. For more information about Isocore visit the web site at http://www.isocore.com.

About Avici Systems

Avici Systems Inc., headquartered in North Billerica, Mass., is a leading provider of purpose-built carrier-class routing solutions for the Internet. Avici's family of routers is designed to meet carrier requirements for the highest scalability, reliability and network availability, while lowering the total cost of building and operating their networks. The company's routing systems provide new IP solutions to some of the world's leading service providers. For more information, please visit us at www.avici.com.

This release contains information about Avici's future expectations, plans, and prospects that constitute forward-looking statements for purposes of the safe harbor provisions under the Private Securities Litigation Reform Act of 1995. Such forward-looking statements are subject to risks and uncertainties, which could cause actual results to differ materially from those anticipated. When used in this press release, the word "will", "expected" and other similar expressions are intended to identify such for ward looking statements. Such risks and uncertainties include, but are not limited to, market acceptance of Avici products, services and enhancements, customer purchasing patterns and commitments, development of the market place, product development and enhancement, intensity of competition of other vendors, technological changes and other risks set forth in Avici's filings with the Securities and Exchange Commission.