Subject: [bmwg] RE: MPLS FRR protection mechanism performance

From: [email-masked]
Date: Sat, 25 Feb 2006 07:56:49 -0500

Hi Durga,

I have forwarded these questions to the mailing list and will respond in a
separate posting.

Scott

-----Original Message-----
From: durga.gangisetti [mailto:[email-masked]]
Sent: Friday, February 24, 2006 12:25 AM
To: [email-masked]
Cc: [email-masked]; [email-masked]
Subject: MPLS FRR protection mechanism performance

Scott,
Hope you are doing great.
I understand you work on protection mechanisms.
May I seek (posting same questions) your suggestion on MPLS FRR protection
performance?

Case-I:
If 100% bandwidth is reserved for the FRR backup tunnels, then there would
be no congestion experienced during the re-optimization interval. However,
additional capacity may need to be allocated in the network, thereby
increasing overall cost.

Case-II:
If less than 100% bandwidth is reserved, then there may be some links that
become congested as a result of FRR switching of primary tunnel traffic onto
backup tunnels until sufficient re-optimization has occurred to relieve this
congestion.

Hence, I strongly believe in bounding the level and duration of such
FRR-induced congestion as important measure of FRR performance. Here is a
heuristic logic for bounding FRR performance for a single link failure:

-The set of failed primary tunnels for the failed circuit link determines
the amount of traffic offered to the circuit links that comprise the FRR
backup tunnel. The largest traffic offered in excess of circuit capacity
divided by the MPLS re-optimization signaling rate upper bounds the worst
case congestion interval. This effectively assumes that all primary LSPs
originate and terminate on the routers on each end of the circuit link.

-A lower bound on the congestion interval assumes that the primary LSP
endpoints are uniformly distributed across all routers in the network. The
worst case ratio of the total traffic offered to circuit speed is worst case
measure of congestion.

Please offer suggestion.

BTW, what do you think of Worst case when dependencies like,
a) Network topology,
b) Cause of Link failure
c) Vendor's signaling rate
a must to consider, how to capture their role in overall performance?

Brgds,
Durga Gangisetti
Network Architecture and Advanced Technologies
UUNET/MCI/Verizon Corporate
Ashburn, VA 20147.

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