Is a router still a router even if forwarding packets is just one of its many jobs?

More and more applications, such as firewalls, VPN concentration, voice gateways and video monitoring, are being piled onto routers. Cisco's Integrated Services Router (ISR), for example, even boasts an optional application server blade for running scores of Linux and open source packages.

"A customer came to us inquiring about all the services on a router but they did not need the routing capabilities," says Inbar Lasser-Raab, senior director of network systems at Cisco. "It's becoming a hosting platform for any service linked or tied into the routing capability."

About a fifth of Cisco's annual $35 billion to $40 billion in revenue is attributable to sales of enterprise and service provider routers. And the worldwide router market in 2008 was just less than $13 billion, according to Dell'Oro Group.

But those numbers might become harder to track as the definition of a router changes.

"Whether you call a particular platform or chassis a router depends on what the thing is primarily used for," says Jeff Doyle, president of consultancy Jeff Doyle and Associates. "Media gateways, firewalls, GGSNs, etc. They might all have router functions in them, but they are generally called by whatever their primary role in the network is."