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Re: node disjoint and SRLG

Subject: Re: node disjoint and SRLG
From: Stewart Bryant
Date: Fri, 26 Nov 2004 18:20:57 +0000

Alia Atlas wrote:

At 06:23 AM 11/26/2004, Stewart Bryant wrote:

What we have not discussed, but which applies in this case, is applying LF to a subset of the prefixes.

The importance of the micro-loop prevention depends on the duration of the possible micro-loops.
Yes, we agree on that.

What Mike and I have always been alarmed at is the thought that in
protecting some subset of the prefixes, we damage - perhaps quite badly- the service to other prefixes unless we have 100% coverage.

The micro-loop prevention can't make the service to other prefixes substantially worse.
If a prefix is not repaired, it is black-holed until we reconverge.
All the LF approaches delay convergence, then those prefixes are
black-holed for longer.

Now what we could perhaps to is to run LF on just the prefixes that
we can protect. So if we knew that we had 100% protection on say
VPN and PWs. We could run controlled convergence on the adresses
of those endpoint address and run uncontrolled on the rest.

Right, but how do we communicate the prefixes that are protected (or unprotected) in a reasonable fashion?
Surely the simplest approach is for the node that issues the LSP to
say "and by the way I am protecting the following IGP paths". That
would take about 1000 bits which is not unreasonable.


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