Hi folks, in drafts draft-ietf-ccamp-gmpls-mln-reqs-00.txt and
draft-ietf-pce-inter-layer-frwk-00.txt the concepts of multi-layer
and multi-region networking are defined and discussed.
An important case is when the IP layer rests directly upon a
"virtual network topology" layer that we will desire to change via
GMPLS signaling. Changes to the IP layer VNT can produce "transient
IP layer routing loops" also known as "micro loops" which can last
100's of mili seconds or more. Hence any time we change a
connection between IP layer routers via GMPLS we can cause
significant outages compared to the recovery times that we set out
to achieve with GMPLS fast reroute and other mechanisms such as SDH
APS (rings and linear).
At the Routing working group, Alex's draft draft-ietf-rtgwg-
microloop-analysis-01.txt provides some analysis and a method to
reduce the impact (duration too) of the transient loops. More
recently the drafts:
(1) draft-bryant-shand-lf-applicability-01.txt
(2) draft-bryant-shand-lf-conv-frmwk-02.txt
(3) draft-francois-ordered-fib-01.txt
Address this problem more generally including in (3) a method that
guarantee loop free convergence.
The problem is that these have generated very little interest at
the RTG WG and may not move forward. This area is not within PCE
or CCAMPs charter but can have an impact on the adoption of GMPLS
in multi-layer/region networking. If you're interested please take
a look and comment to the RTG WG. Note I wasn't involved with
writing these, but came across them when considering the effects of
GMPLS changes on the IP layer VNT.
Thanks
Greg B.
--
===================================================
Dr Greg Bernstein, Grotto Networking (510) 573-2237
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