Re: [mpls-tp] Proposed liaison to ITU-T on G.8110

Support...

D 

-----Original Message-----
From: mpls-tp-bounces@ietf.org [mailto:mpls-tp-bounces@ietf.org] On Behalf Of Stewart Bryant
Sent: Monday, June 28, 2010 1:42 PM
To: mpls-tp@ietf.org
Subject: [mpls-tp] Proposed liaison to ITU-T on G.8110

Several people have pointed out a discrepancy in the model for MPLS as documented in G.8110. Since this formal model plays a major role in the ITU-T MPLS-TP G.8110.1 specification, the error should to be corrected before publication.

I therefore propose that we send the following liaison to the ITU-T.

- Stewart

===============

To: ITU-T WP3/15
From: IETF

Dear Dr. Trowbridge,

We note that G.8110 is referenced as a normative reference from the draft text of the revision of G.8110.1. We also note that G.8110 is now five years old, and has received no contributions for update over that period. G.8110 has been described as "not covering all of MPLS and certainly not what has happened in the last five years."

We believe that G.8110.1 should document MPLS-TP accurately. It is important, therefore, that where the model for MPLS-TP differs from that described in G.8110, the correct model be developed and documented in G.8110.1.

We would like to draw your attention in specifically to Section 6.2.2 of G.8110 (and, in particular, Figures 1 and 2) that says that the Time-To-Live (TTL) field of an MPLS header is part of the Characteristic Information (CI) of an MPLS_CI traffic unit. We note that according to G.805, the CI is supposed to be delivered end-to-end between MPLS APs without modification or inspection. But the function of a TTL in an MPLS-TP network is to be decremented at each hop along the path, and to be inspected at each hop and tested against zero. Thus, in the model for MPLS-TP, the TTL should not form part of the CI.

We request that G.8110.1 be updated to include this revision to the model. This might most easily be achieved by augmenting the references to G.8110 with updated figures based on those in G.8110 along with appropriate text explaining the differences in the model such that
G.8110.1 correctly captures the model for MPLS-TP.

==========
_______________________________________________
mpls-tp mailing list
mpls-tp@ietf.org
https://www.ietf.org/mailman/listinfo/mpls-tp