Industry readies for optical, IP convergence

By Jim Duffy, Network World |  Networking

ATLANTA -- The worlds of IP routing and optical switching are fast converging, if last week's NetWorld+Interop 2000 is any indication.

Optical networks were on the lips and minds of many attendees, from the largest makers of equipment for service providers to the smallest start-ups tucked away in the farthest reaches of the vast Georgia World Congress Center exhibition hall.

For users, the convergence of the IP and optical worlds could affect the speed and price at which next-generation services are offered. Virtually all multimedia IP services being provisioned or planned rely on the integration of IP and optical networks, observers say.

But there are many open issues regarding the convergence of IP and optical. Among them are who should "own" the intelligence of the optical network -- router vendors or optical switch vendors? Another is coordination of signaling and control plane functions between routers and optical cross connects.

There are also contrasting viewpoints on how many electrical-to-optical conversions are necessary in an IP optical network, and where in the network these conversions should occur.

"The big question is, what's going to make the end-to-end decisions, the router or the switch? There are fundamental religious wars here," says Shaym Jha, a vice president at Corvis, a maker of optical add/drop multiplexers, switches and other gear.

Corvis believes in keeping optical switching and routing decisions separate, yet making both control plane functions interoperable.

"Switching should be left to the optical network," Jha says. "IP companies live in the routed world. What doesn't make sense is the router telling the switch which route to take."

Yet the brains for optical switches haven't been entirely baked yet, Jha admits. Switching and routing control functions for optical network bandwidth provisioning as well as route restoration and protection are still evolving in the Optical Internetworking Forum and the International Telecommunication Union, he says. The Optical Domain Service Interconnect coalition is also working on optical signaling standards.

"Control in the optical network is being worked out as we speak," Jha says.

The Internet Engineering Task Force's Multi-protocol Label Switching (MPLS) specification is viewed as one key way to coordinate the signaling and control plane functions between IP routers and optical switches. Indeed, some optical standards bodies are devising a Multi-protocol Lambda Switching (MP Lambda S) protocol to engineer traffic in optical networks the same way MPLS steers traffic in routed nets.

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