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

Stewart,

That seems like a very reasonable liaison.

Cheers,
Andy

On Mon, Jun 28, 2010 at 1:42 PM, Stewart Bryant <stbryant@cisco.com> wrote:
>
> 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.
>
> ==========
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