The stackable switch router (SSR) uses the same architecture as Avici's TSR core router but fits in just half of a standard equipment rack. Like the TSR router, the SSR is intended for the network core, but is tailored for service provider points of presence that don't require TSR bandwidth or don't have the physical space for a multirack system.

"We had existing customers that were suggesting to us that we give them a smaller form factor," said Pete Chadwick, vice president of marketing for Avici Systems, based in North Billerica, Mass. "We believe this will fundamentally double our addressable market."

"Stackable" means two SSRs can be placed on one rack, where the network will treat them as a single element.

Juniper Networks was the first of the core-router vendors to miniaturize its boxes, introducing the M5 and M10 in September 2000. Targeted at the network edge, both systems are based on the same architecture as the company's high-end routers, such as the M160.

Cisco Systems followed suit a year later, claiming that demand was rising for IP services on the network edge. Last month, Cisco introduced its 12404 Internet Router, based on the 12000 series of core routers. Cisco also rolled out the 10720 Internet Router targeted specifically at metro networks.

Unlike Juniper and Cisco, Avici contends its smaller router is still aimed at the network core. The company has no plans to develop specialty edge or metro boxes, Chadwick said.

"We felt there were lots of edge players — Cisco, Riverstone, Unisphere. There are a lot of players who have pretty good boxes at the edge," Chadwick said. "The carriers we talk to don't have any problem saying they're going to use Unisphere at the edge and Avici at the core."