Subject: l2vpn-vpls-multi-homing-01.txt

From: "UTTARO, JAMES, ATTLABS" <[email-masked]>
Date: Wed, 30 Jul 2008 03:07:43 -0400

The current approach being used to accomplish leaking "multi-homed"
information between AS's is too tag the primary with some CV and then
take action as it crosses the AS boundary ( set LP ).. The draft seems
to take the approach of mapping the LP to a VE preference for a route (
VE-ID) in the local AS ( AS1). The advantage of the first solution is
that a route may be leaked across multiple AS boundaries. As the CV
remains ( transitive ) I can always key off of it to set  LP in the
current AS domain. How can I accomplish this with VE pref? Is it kept as
the route transits through multiple AS? I assume that VE pref is
transitive and not reset upon re-advertisement from remote AS2 to remote
AS3. 
 
It states for "BGP Path Selection" that ADs with the same exact <RD,
VE-ID, VBO> are candidates for BGP Path Selection.. In our network we
use unique RDs to reduce convergence time for primary/backup. Our
approach is to ensure that both the primary and backup sites are opaque
to the BGP topology. In this way both routes are sent to all PEs
participating in the L2VPN. So how would a receiving PE treat to routes
that have the same VE-ID but different RDs? The draft states the they
would not be candidates for "BGP Path Selection". This implies I cannot
manipulate LP to select a primary when I use unique RDs. This definitely
is in conflict with our fast convergence goals for our L2VPN customers.
 
Jim Uttaro