The IETF and ITU standards bodies are sparring over a set of MPLS specifications that some say could lead to massive interoperability issues for service providers if left unchanged.

The Internet Engineering Task Force (IETF) is at odds with the International Telecommunication Union (ITU), over a special transport network architecture that the ITU’s Telecommunication Standardisation Sector (ITU-T) is developing, to allow Multiprotocol Label Switching (MPLS) traffic to run over an Ethernet backbone. Among the network equipment vendors that have been contributing to the development are Alcatel-Lucent, Ericsson, Fujitsu and Tellabs.

The problem, according to the IETF, is that the ITU’s Transport-MPLS (T-MPLS) specification will not work with the billions of dollars in routers and switches that carriers have installed in recent years, based on the IETF’s MPLS standards.

"The situation is catastrophic," says Stewart Bryant, IETF liaison to the ITU-T on MPLS issues and a technical leader at Cisco. "There’s a fundamental opportunity for a major train wreck" between the IETF’s MPLS and the ITU-T’s T-MPLS.

Bryant says the problem is that T-MPLS uses the same EtherType as MPLS, which will lead to confusion in operational networks. An EtherType is a field in the Ethernet network standard that indicates which protocol is being transported.

"If you think about a piece of network equipment, it looks at the EtherType and that tells it how to process the packet. The EtherType is the same for MPLS and T-MPLS, so we are extremely unhappy about that. T-MPLS should use a different EtherType, ideally called T-MPLS so there is absolutely zero confusion in dealing with T-MPLS or MPLS traffic," Bryant explains.

“Our concern is that there should be absolutely nothing designed, implemented or specified that risks the deployed base of MPLS equipment,” Bryant adds.

T-MPLS is being developed by the ITU-T’s Study Group 15 Working Party 3, which considers optical trans port network structure. This group has been developing T-MPLS for three years and has finalised four specifications, including an architecture document, a network-to-network interface, an equipment specification and a switching document. The ITU-T says service providers need a special profile or subset of MPLS to meet their requirements and that’s why they are developing T-MPLS. For example, T-MPLS will support more robust operating environments and messaging (OE&M) and protection switching than is provided by the IETF’s MPLS standards.

ITU-T leaders deny that T-MPLS will create interoperability problems for the Internet, let alone catastrophic ones.

"I have a pretty good degree of confidence that we haven’t put anything into the T-MPLS standard so far that’s going to cause massive interoperability problems," says Stephen Trowbridge, chairman of Working Party 3 of Study Group 15. Trowbridge, who works for Alcatel-Lucent, says "T-MPLS will stay in the service provider network, and the customer network doesn’t use it."

Trowbridge called the T-MPLS flap a "turf war" between the IETF and the ITU-T, and he says emotions were running high among the members of the two standards bodies.

"This is sort of a contentious area," Trowbridge says. "Everything is converging. You see more and more optical technology further toward the edge of the network. You see more and more packet technology moving toward service provider networks….Turf battles are inevitable."

The T-MPLS working group will hold a week-long meeting in Stuttgard, Germany starting Sept 10, and several IETF leaders will attend the meeting in an attempt to hammer out a solution. Around 40 representatives from carriers and network equipment vendors plan to attend.

After the meeting is over, the ITU-T will send a letter to IETF leadership outlining what decisions Working Party 3 has reached regarding the future direction of T-MPLS.