IETF, ITU will work together on new transport protocol
The Internet’s leading standards bodies have agreed to work together to ensure that a new transport protocol being developed for Multiprotocol Label Switching networks is compatible with the billions of dollars worth of MPLS equipment that carriers have installed in recent years.
The Internet’s leading standards bodies have agreed to work together to ensure that a new transport protocol being developed for Multiprotocol Label Switching () networks is compatible with the billions of dollars worth of MPLS equipment that carriers have installed in recent years.
The International Telecommunication Union (ITU) and the Internet Engineering Task Force (IETF) have agreed to work “in close collaboration” on Transport-MPLS, according to a report from a recent meeting attended by representatives of both groups. The meeting was held in Stuttgart, Germany, from Sept. 10 to 14.
“The agreement so far is to form this joint working team of experts to ensure that problems can be avoided going forward, but many of the details are still to be worked out,” says Stephen Trowbridge, chairman of the ITU’s Telecommunication Standardization Sector (ITU-T) Working Party 3 of Study Group 15, which is developing T-MPLS.
The final decision on how the two groups will work together on T-MPLS will be considered at a February 2008 meeting of the ITU-T’s Study Group 15.
“Whilst productive discussions took place and a proposal was drafted, it is my understanding that a number of other ITU-T groups have to consider the matter,” explained Stewart Bryant, IETF liaison to the ITU-T on MPLS issues and a technical leader at Cisco. “It is also my understanding that the ITU process then requires the recommendation of [four related study groups] to be ratified at a plenary before they can be considered definitive output for consideration by ITU-T management.”
The IETF leadership and its sister organization, the Internet Architecture Board, also need to review the proposal for the joint T-MPLS working group, Bryant added.
The joint meeting “was a good first step” in resolving the IETF’s concerns about T-MPLS, Bryant says.
“The scope and authority of this particular meeting was limited, and we still need to see broad acceptance and ratification in both the IETF and the ITU of its recommendation in order to know if we truly made progress,” Bryant added.
T-MPLS is a controversial transport network architecture that the ITU-T is developing to allow MPLS traffic to run over an Ethernet backbone.
The crux of the problem between the ITU-T and the IETF is that T-MPLS uses the same EtherType as MPLS. An EtherType is a field in the Ethernet networking standard that indicates which protocol is being transported.
The IETF, which developed the original MPLS specifications, said T-MPLS as currently envisioned by the ITU-T would cause massive interoperability issues for carriers that had already installed MPLS routers and switches.
The ITU-T says the situation is fine because MPLS and T-MPLS will be used on networks that don’t connect to each other.
Nonetheless, the ITU-T has agreed to begin cooperative work with the IETF on T-MPLS “as soon as possible,” the report says.
“The IETF and ITU-T will work in close collaboration on T-MPLS toward solutions that ensure MPLS/T-MPLS compatibility, consistency, and coherence, recognizing that the sole design authority for MPLS resides in the IETF, and the domain of expertise for Transport Network Infrastructure resides in ITU-T [Study Group] 15,” the report says.
The new joint working group of MPLS and T-MPLS experts will decide how to progress on T-MPLS development. Anyone from the ITU-T or IETF may participate in the joint working group, which will conduct its work via e-mail correspondence and conference calls.
“The hope is that the joint team of experts should put an end to the turf war” over T-MPLS, says Trowbridge, who works for Alcatel-Lucent. “Those who care about how T-MPLS evolves should participate in the joint team rather than participating only in one of the standards groups and complaining about what the other standards group is doing.”
The chair and the members of the joint working group have not yet been appointed, nor has a first date for a meeting been set, Bryant says.
The report says the new group’s first task is to review the ITU-T’s T-MPLS specifications to see whether any inconsistencies, incompatibilities or omissions are found with regard to the IETF’s MPLS technology. Any problems that are found will be resolved either by generating new MPLS-related work in the IETF or by amending the ITU-T’s T-MPLS recommendations.
“The working team will be responsible for identifying and recommending what aspects of the requirements, solutions and architecture should be formally documented in IETF [Requests for Comments] using the IETF standards process, or ITU-T Recommendations using the ITU-T process,” the report says.
The report says the joint working group will consider the following aspects of T-MPLS and MPLS:
* forwarding plane,
* operations, administration and maintenance (OAM),
* control plane,
* network survivability and
* transport equipment and network managements.
Trowbridge is optimistic that the joint working group can resolve the IETF’s concerns about T-MPLS causing interoperability problems with installed MPLS gear.
“The fears of interoperability problems were more related to speculation about [how T-MPLS] might evolve than what is in the first version of ITU-T specifications,” Trowbridge says. “In the first version, T-MPLS carries a single client type [Ethernet], and while it is true that MPLS can be a client of Ethernet, this keeps the relationship strictly as client/server. The joint team of experts should ensure that if the technology evolves in a direction that allows direct peering of MPLS and T-MPLS, that this will be done in a way that avoids interoperability problems.”
The IETF says there is still a lot of work ahead for the two groups to make sure that T-MPLS doesn’t cause a “major train wreck” on the Internet, as Bryant had feared.
“What is most important to the industry is that T-MPLS be compatible, consistent and coherent with the IETF MPLS technologies,” Bryant says. “All those present at the [Stuttgart] meeting agreed with this principle, and indicated commitment to bringing the MPLS and [Pseudowire Emulation Edge to Edge] related work into the IETF to ensure that this is achieved.”
