Virtual Network Topology (VNT) changes and IP layer routing loops

[Greg Bernstein <gregb@grotto-networking.com>]

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