Subject: draft-iwata-mpls-shared-fast-reroute-00

From: "David Allan" <[email-masked]>
Date: Mon, 6 Aug 2001 13:32:27 -0400

A simple question (which I did not get a chance to ask in the meeting
today):

When the "Backup LSP trigger" message is issued up the primary path, should
it not also contain an ERO object for the primary path as well as the first
backup route.

Seems to me I should care a whole lot about the tributaries to the shared
backup being diverse with the primary path. (I'll call them tributaries as I
couldn't find a specific term for them). Right now I do not think I can make
that statement unless every LSR in the primary path retains ERO information
(in order to verify this when performing the shared path computation), and
it would not currently (IMHO) have reason to do so.  So my shared path
computation becomes, "shortest path to the first backup LSP that is route
diverse with the primary LSP".

This is really a separate issue from the suggestion that there is no shared
path computation required, and the backup LSP from any LSR in the primary
path simply be opportunistic in merging with any other backup paths for the
same LSP encountered along the optimal backup route. This would appear to
have the same effect as constantly updating the ERO propagated with the
"backup LSP trigger" after the establishment of each backup tributary.

BTW, I'm inclined to note that if there is any resource committment
associated with these LSPs, it makes 1+1 look positively frugal. Perhaps we
could invest some effort in fault propagation efficiency and save a whole
lot of bandwidth....

cheers
Dave