Subject: Can RSVP-TE shortcut an ERO?

From: David Charlap <[email-masked]>
Date: Tue, 19 Aug 2003 12:22:14 -0400

Given the following topology:

  R1 ---------------- R2
    \                /
     ------R3--------

R1 receives a Path message with an ERO that looks like:

	R1
	R3 (loose)
	R2

When R1 does a route-table lookup to resolve the address of R3, suppose 
it gets one of R2's addresses as the next-hop (maybe a link is down, or 
there's administrative weighting involved or something.)

R2 receives the Path message with the following ERO:

	R2
	R3 (loose)
	R2

It now forwards the Path to R3, which then has to reject it (with 
PathErr) because the next-hop back to R3 is along the link the Path came 
in on, and we can't create loops.

The question is: Is R2 allowed to simply terminate the tunnel when it 
receives the first Path message (ignoring the remaining ERO subobjects) 
or does the presence of ERO subobjects force it to generate a new Path 
message?

-- David