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Hi, Ali:
Thanks for your comments in the last L2VPN WG
meeting, I will try to give you some reasons here.
Following are the two
questions:
1. What do you think will be faster
convergence? When you flush MAC addresses,
the learning is done in data plane at wire
speed. Why does that prolong convergence time?
-Faster convergence means the time to
associate the MACs with the "exact" out port
will be shorter. Though learning is done in
data plane at wire speed, the time for a frame to arrive
at the end host and the response time for a
host to send a reverse frame accross the PE (on which the
MACs is flushed) will be a rather long
time. So the learning process is not only determined solely by
the wire speed, but also on the host processing time and delays on
all the intermediate routers.
For this reason, flooding may also last for a
rather long time.
2. You consider a simple case with simple
backup for primary. In cases where primary fails and traffic
gets
distributed among multiple PE's, how do you take care of that? -I believe the most commonly
deployed scenario is one backup PE for a primary PE.
In my opinion, for the scenario of multiple
backup PEs protecting a primary PE,
only one PE out of them will be elected as the
working PE when the primary PE failed,
rather than distribute the traffic over
multiple backup PEs,
otherwise, loops may be introduced to the
attached customer site.
BTW, in a similar way, for PW redundancy
mechanism, only 1 secondary is selected as the working PW (see
draft-ietf-pwe3-redundancy-bit-00.txt
in PWE3 WG)
Anyway, if there is any such requirements
confirmed, I think it will be Oill be OK for us to find some solutions and
add them to the future
drafts.
cheers,
Yuanlong
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