Subject: Work on IP fast rerouting in IGPs

From: Alex Zinin <[email-masked]>
Date: Fri, 16 Apr 2004 16:33:59 -0700

Folks-

 As many of you know, the topic of fast rerouting in IP (as opposed to
 MPLS-based FRR) has been brought up several times at the IETF meetings recently
 (see reading material at the end of the message).

 I believe that this work is important and there's even some room for
 standardization here. More specifically, even though the exact algorithms of
 route calculation in IGPs are historically non-normative, the criteria, such as
 shortest path first, are. Forwarding packets along the feasible (non-SPT, but
 loop-free) next-hops, strictly speaking violates those, and if done incorrectly
 is likely to lead to routing loops. Hence, the need to standardize at least the
 criteria for feasible next-hop calculation and document possible algorithms for
 informational purposes (pretty much the way OSPF and ISIS do this.)

 Per above, I would like bring this work to the RTGWG and ask the IESG to add
 a corresponding item to its milestone.

 Regarding specific proposals. It seems that Alia's work could be used as a good
 basis. However, I am quite dubious about the U-turn part. I wouldn't feel
 comfortable including U-turns in the standard-track specification. At most, we
 could have an experimental document for this part.

 I will be sending a similar message to RTGWG next week, so comments are
 appreciated.
 
 Reading material:
  - Cengiz's slides at 55th IETF http://www.packetdesign.com/news/presentations/2002/fast-reroute6.pdf
  - Alia's slides at 59th IETF http://www.ietf.org/proceedings/04mar/slides/rtgarea-2/index.html
    Alia's draft: draft-atlas-ip-local-protect-00.txt
  - Early draft http://www.potaroo.net/ietf/old-ids/draft-kini-traf-restore-nsp-00.txt
 
-- 
Alex