Front Page: GMPLS Weds Optical and Edge

The user network interface (UNI) interoperability event that the Optical Internetworking Forum staged at SUPERCOMM 2001 was an important first step toward the widespread implementation of GMPLS (see xchange May 15, page 8). But more work is on the horizon.

GMPLS was designed to allow edge networking products like routers and switches to request bandwidth from the optical layer. It's also intended to make the optical network more dynamic by adding intelligence to optical elements such as optical cross-connections, which are relatively "dumb" today, explains Yves Lemaitre, vice president and general manager of core data products at Alcatel, which already sells cross connects and ATM switches based on GMPLS as it is defined.

More intelligent optical devices could help network operators to do better restoration and better utilize bandwidth. "Today, optical products don't really talk to each other as routers do," Lemaitre says. GMPLS is an attempt to apply some concepts routers use to the optical layer.

GMPLS also will give routers additional information about the optical network, says Phil Francisco, vice president of marketing at PhotonEx Corp. For example, enabling a router to understand the health of various routes on the optical network can allow those routers to make requests of switching points to an optical cross connect, he says.

Francisco says the Internet Engineering Task Force and OIF are extending link management protocol (LMP). LMP is what a router uses to decipher the availability of a link between itself and another router.

"When you look at the optical network as a black box, you may assume all routes are open," he says, adding that's not necessarily true.

PhotonEx took the lead on adding to the LMP the lengths of various routes, which can affect delay issues. The IETF and OIF have adopted that suggestion into their GMPLS work, Francisco says, explaining that the PhotonEx submission also adds to the LMP fields to show how full a particular link is and to provide information about link failures downstream in the network.

The new standard's impact on operational support systems (OSSs) is another GMPLS aspect that remains to be addressed, says Francisco. PhotonEx expects to do the first customer shipments of its PX-Ultra high speed DWDM system by the end of the year. The industry is working to understand what OSS equipment is needed to support these almost self-directed GMPLS networks with the least human intervention.

GMPLS is not only the relationship between the optical layer and IP devices like routers, explains Sab Gosal, director of product marketing at Polaris Networks Inc.

GMPLS also addresses TDM switch capability, packet switch capability, lambda switch capability and fiber switch capability.

During the fourth quarter, Polaris will make a multilayer, multirate optical transport switch available for trial.

"It's all about creating a unified control plane for all these types of equipment," Gosal says.

Correction:

An incorrect secondary headline accidently was inserted underneath the correct headline reading "MPLS Gets Real" in the September issue of xchange page 26.

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