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Re: questions on draft-bryant-ipfrr-tunnels-01.txt

Subject: Re: questions on draft-bryant-ipfrr-tunnels-01.txt
From: Stewart Bryant
Date: Fri, 26 Nov 2004 17:30:08 +0000

Alia Atlas wrote:

At 06:44 AM 11/26/2004, Stewart Bryant wrote:

MPLS RSVP/TE FRR is loop free in the presense of unknown SRLG.  At
worst the fast restoration fails and a new LSP is needed from ingress
to egress.  So the worst case is a slow restoration but not a loop.

How is this achieved? Presumably by excluding from the set of packets
that can be repaired and packet with a label that indicates that it is
part of a repair tunnel.

If we were to always tunnel to the other side of the failure we
could do the same sort of thing in IPFRR, but prefer to sent
the packets native. We could however mark the packet as being
repaired somehow (TOS bit perhaps) and then refuse to re-repair it.

I think that if the point where a repaired packet re-joins the SPT is always a downstream path, then we could have the same property. Unfortunately that does limit coverage a bit.
The assertion was that MPLS RSVP/TE FRR is unconditionally LF against
unexpeceted SRLG.

|                                 |

AB breaks and unexpectedly FE breaks. What stops the loop?


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