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Re: BGP TE attr last call by softwires WG (2nd question)

Hi again Yakov,

Thanks also for the reply to my second question.
Your answer seems to imply that the applicability of your work is strictly limited to L1VPNs.
If this is the case, we can easily close this discussion by adding text to the Abstract and Introduction such as: 

 The scope and applicability of this protocol extension is
 currently limited to single-AS deployment scenarios of the
 basic mode of L1VPNs. Further applications are for
 future study, but these mechanisms SHOULD NOT be
 used in any attempt to support TE aggregation.

Cheers,
Adrian


2. There is more than one AS

   Consider

     CE1--PE1...AS1...ASBR1--ASBR2...AS2...PE2--CE2

   PE2 advertises reachability to CE2 and includes TE
   information. The TE attribute is non-transitive so it is
   not just passed on, but ASBR2 wants to announce
   reachability to CE2 (in the VPN case, we may want to
   support a multi-AS VPN).

   So ASBR2 can advertise reachability to CE2, but what TE
   parameters does it advertise? The parameters for the
   link PE2-CE2 are not so helpful because the TE
   reachability across AS2 may be different. Yet any attempt
   to perform a computation of the TE reachability across
   AS2 (i.e. TE aggregation) is complex and potentially
   unstable. (Of course, if a tunnel is pre-established
   between ASBR2 and PE2 this is a different matter.)

I think that these two different scenarios need attention
in the I-D.

For the first one, it may just be a matter of indicating
which approach is to be used.

For the second one, I hope the answer is to recommend
against any form of TE aggregation. This could easily be
added to section 4, and I would be happy to provide text.
BUT, it will still leave open the question about if and how
TE information is propagated beyond the AS.


For the second one the answer is in rfc5251:

  Consideration of inter-AS and inter-provider L1VPNs requires further
  analysis beyond the scope of this document.