AVICI SYSTEMS SCHEDULES FIRST QUARTER EARNINGS RELEASE DATE AND TIME

N. Billerica, MA, April 10, 2006 — Avici Systems (Nasdaq: AVCI), today announced it will release financial results of its fiscal first quarter ended March 31, 2006, on April 20, 2006 and will host a conference call on April 20 at 8:30 a.m. EST, to be broadcast live over the Internet.

To participate via telephone, the dial-in number is 877-209-0397. Please call ten minutes prior to the scheduled conference call time. For live Webcasting, go to the Avici Web site at www.avici.com and access the investor relations section, clicking on either the live Webcast link or the microphone icon to listen.

The conference call will be archived on the Avici Web site. A replay will be accessible by telephone after 1:00 p.m., for approximately 48 hours afterward. To replay the call dial 800-475-6701 using the access code 825121.