Subject: RSVP: Proper behavior when an interface goes down

From: David Charlap <[email-masked]>
Date: Tue, 13 Jun 2000 20:03:56 -0400

When an interface goes down (either administratively or otherwise), and
there is an outstanding RSVP-TE session (path and maybe resv) on that
interface, what specifically shoudl happen.

Obviously, any Path and Resv that was received on that post should be
torn down.  (Possibly after a delay, to dampen the effects of possible
interface flapping.)

What I'm unclear on is if a PathErr should be sent as well.

If a Path arrives with an ERO object, and there is no route to the
next-hop in the ERO, a PathErr message is sent out (with Routing Problem
as the error code and and an appropriate error value).

Now, if there is a Path already established, and the outgoing interface
goes down, such that the next-hop from the ERO is no longer reachable,
should the switch send this PathErr message back to the sender?

Or should it do nothing and rely exclusively on the local IGP to
propagate the network topology change back to the sender, which can then
take action (like initiate a make-before-break reroute, or something
else.)

-- David

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From: Markus Jork <[email-masked]>
Date: Tue, 13 Jun 2000 20:47:00 -0400

David,

> take action (like initiate a make-before-break reroute, or something

Sending the PathErr message immediately is the right thing to do
because it provides the tunnel ingress with timely feedback that the LSP
went down.

Markus