Internet Architecture Board


September 2005

ITU NGN Liaison Report

Scott Brim
10 September 2005

NGN Focus Group

The NGN Focus Group just finished their second-to-last meeting. There will be one more to do final tweaks on the 17 or so documents they are handing over, finished or not, for use by the Study Groups. The FG itself will close, but there will be quarterly meetings where all the NGN-related Questions, from all Study Groups, can get together and work on NGN issues. These are called the “NGN Global Standards Initiative” (NGN-GSI).

Scope, Requirements, and Functional Architecture

A number of people are making sure that the conceptual framework for “NGN” is not just IMS, and that it includes services like plain old Internet connectivity and on-path signaling (like RSVP) — also that services can be decoupled from the network that carries them.

NGN Release 1 does not require that an “NGN” connect to the Internet, since they are not sure what should be in a border agreement. There was some diiscussion about what happens to existing subscribers. It was agreed that existing subscribers must not lose Internet access, but it’s not clear how the network operators are going to ensure that.

There were some IEPREP-type requirement details that I can’t evaluate. They may just be terminology. If someone wants to take a look, let me know.

Working Group 7 (future packet-based network) has essentially finished. From an IETF view, it is all straightforward except for two things: first, they strongly recommend off-path (not just path-decoupled) signaling, and second, in diffserv they want to distinguish “urgent” traffic from “important” traffic (traffic that doesn’t have to get there quickly, but it must get there).


SG13 is “the NGN Steering Group” and will be inheriting most of the output from the Focus Group in November.

Liaisons from the IETF

They went over two. First the one following up on the joint workshop (this is the first SG13 meeting since the workshop), and second the one to SG13 (and other SGs that might interact with the IETF) expressing concern about some contributions.

The first had no comment. The second was well-received. The SG13 chair interpreted it to the group, suggesting early engagement and the equivalent of early review. My notes: “It is noted that inputs are not the main results, it is the outputs that are important. Rapporteurs: if you identify issues that might infer additions to IETF protocols, etc, please write a liaison to the IETF advising them on studies and possible requirements. Then if we have a real requirement we can draft an ID, submit it through the liaison process, and some of us can attend an IETF meeting.” The contributions the liaison particularly mentioned were in Questions 4 (QoS) and 9 (IPv6). See below. SG13 as a whole is responding with a liaison back to the IETF affirming cooperation.

After meeting with Brian Carpenter about the liaison on the last morning, ITU-T Director Zhao told the group that (my notes):

ITU can’t do everything but the ITU needs to keep our competence and our relevance to the market. If the ITU-T is only about ideas and don’t offer complete results that satisfy our members, then it will be irrelevant. This morning Brian Carpenter came over. He called on me several times for a meeting. We noted the liaison statement. We got a good impression from Brian Moore that cooperation between ITU-T and IETF is very important. We encourage all possible cooperation. We got agreement from the chair of the IETF that they have their competence, we have our competence. We can do protocols as well. Each will respect the other. We have to keep communication channels open. Not necessary to use formal liaison statement. Not necessary to always have to remind each other that we should respect each others boundaries etc. I am glad that an ITU-T delegation was able to participate in the IETF in Paris, despite some theft problem. I encourage that we continue to have cooperation, and the ITU-T supports cooperation between ITU-T and IETF and others, for example TISPAN.


Y.vpndecomp models VPNs of all sorts. It was “consented” at this meeting. I don’t know if it’s exactly aligned with similar IETF activities but it did not seem to go against any.

Q4 (QoS)

Two contributions followed on to the BT ones on flow-based QoS presented last time. They were reminded that when the subject is IETF protocols, to stick to requirements, architecture and protocol selection (essentially what the IETF and ITU-T have agreed on). Their text is still in a living list for the Question.

Q7 (interworking)

Since this overlaps PWE3, L2TPv3 and MPLS, a bit of detail …

A corrigendum for Y.1413 “TDM-MPLS network interworking — User plane interworking” was finished.

Y.1414 is voice over MPLS with AAL2. They requested a PW type a while ago, the IETF asked for evidence of demand or implementation, and no one has stepped forward, so it’s not being pushed.

A significant document is starting on principles of interworking. It will probably be primarily about pseudowires, but it includes management and control plane as well, and extends to other areas like PSTN-VoIP.

Q9 (IPv6)

They changed all their documents to clarify that they are not trying to define protocol extensions on their own. They composed a liaison to the IETF (later assimilated into a general SG liaison) on what they are trying to do and where they want to collaborate. They are interested in bringing drafts to the IETF but want some help. I encourage anyone in Europe with clue about IPv6 to come to the SG13 meetings (January and July) to help out.

As part of encouraging their bringing their issues to the IETF, now, I invoked the concept of early review, and told them that it would be better to work out solutions together, rather than waiting until their idea of a solution was fixed in their mind, such that they felt they had a requirement for their particular solution.

Their report says:

The liaison statement from IETF (TD 90(PLEN)) was reviewed with some positive comments. It was raised that the IETF wants early engagement and early review of working documents for joint collaborations. The meeting agreed to send the Liaison statement to IETF for collaborations in order not to overlap the works on IPv6.

Please see the combined SG13 liaison, which should arrive in a few days.


… is working in parallel/coordinating with the MFA Forum on MPLS/ATMorFR control plane interworking. Both of them will intersect with PWE3 as PWE3’s work has been expanded.