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RE: OPS-DIR review for: draft-ietf-mpls-ldp-interarea-03.txt

2008-04-28 06:49:07
Thanks. Looks good to me.

Bert Wijnen

-----Oorspronkelijk bericht-----
Van: bruno(_dot_)decraene(_at_)orange-ftgroup(_dot_)com
[mailto:bruno(_dot_)decraene(_at_)orange-ftgroup(_dot_)com]
Verzonden: maandag 28 april 2008 14:07
Aan: bertietf(_at_)bwijnen(_dot_)net
CC: ietf(_at_)ietf(_dot_)org; ina(_at_)juniper(_dot_)net; 
jeanlouis(_dot_)leroux(_at_)orange-ftgroup(_dot_)com
Onderwerp: RE: OPS-DIR review for: draft-ietf-mpls-ldp-interarea-03.txt


Inline,

Bruno

De : Bert Wijnen - IETF [mailto:bertietf(_at_)bwijnen(_dot_)net]

Inline

Bert Wijnen

Van: bruno(_dot_)decraene(_at_)orange-ftgroup(_dot_)com


Bert,

Many thanks for your comments.
More inlined.

Bruno

De : Bert Wijnen - IETF [mailto:bertietf(_at_)bwijnen(_dot_)net]

Forwarding to IETF wide list and authors/editors

Bert Wijnen

Van: Bert Wijnen - IETF [mailto:bertietf(_at_)bwijnen(_dot_)net]


I reveied this document for the OPS Directorate

In general, I think the document is ready for publication.

In sect 7.1 I read:

   For the successful establishment of end-to-end MPLS LSPs
whose FEC
   are aggregated in the RIB, this specification must be
implemented on
   all LSRs in all areas where IP aggregation is used. If
an LSR on the
   path does not support this procedure, then the LSP
initiated on the
   egress LSR stops at this non compliant LSR. There are no other
   adverse effects.

I think/hope (but it would be good to see this confirmed)
that this does
not mean that all LSRs in the set of IGPs that are involved
need to be
upgraded with the new protocol at exactly the same time.

The way I understand it, one can upgrade the LSRs at
different times,
but should only activate this new mechnaism once all LSRs have
ineeded been upgraded with the new capability.

You're right: all LSRs do not need to be upgraded at the same time:
- deployment in each IGP (area) is independent
- LSRs can be upgraded at any time in any order,
- This new mechanism can be activated on the LSR at any time in
any order, (upgrade and activation can be done at same step if
it's considered easier)
- Then, if the FEC/LSP were used, we need a non disruptive deployment:
  (As a reminder, the ABRs used to leak all specific prefixes
in the IGP area.)
  The ABRs can advertise the (new) aggregate prefix at any
time and any order.
  However, the specific prefixes in the IGP area should only
be withdrawn (by the ABRs) once all the LSR of this IGP area have
been upgraded. (Otherwise "If an LSR on the path does not support
this procedure, then the LSP initiated on the egress LSR stops at
this non compliant LSR.")

Do you think this should be clarified in the document?


Up to you.
Apparently I understood it correctly.
The fact that is it not needed to upgrade all at the same time
is the important point for me. If I had understood it incorrectly,
I would have had a bigger concern.

So would I.

Making it clearer is always good I think. Up to you.

I've updated the section 7.1 "Deployment considerations" with the
following:

"This extension can be deployed incrementally:
-     It can be deployed on a per area or routing domain basis
and does not necessarily require an AS wide deployment. For
example, if all specific IP prefixes are leaked in the IGP
backbone area and only stub areas use IP aggregation, LSRs in the
backbone area don't need to be compliant with this document.
-     Within each routing area, LSRs can be upgraded
independently, at any time, in any order and without service
disruption. During deployment, if those LSPs are used, one should
only make sure that ABRs keep advertising the specific IP
prefixes in the IGP until all LSR of this area are successfully
upgraded. Then, the ABRs can only advertise the aggregated prefix
and stop advertising the specific ones."

Please feel free to amend/correct/comment if needed.

Bert

Nits:

Thanks.
All corrections are done and will appear in the next revision.

Thanks,

Bert



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