Subject: Review Call: draft-atlas-ip-local-protect-00.txt as WG item

From: Alex Zinin <[email-masked]>
Date: Thu, 29 Apr 2004 13:05:09 -0700

Folks-

 As discussed in Seoul, draft-atlas-ip-local-protect-00.txt is being considered
 for becoming a WG item.

 At this point I would like to solicit opinions on the following points:

  1. Technical comments on the substance of the document

  2. More specifically, comments on the U-Turn part (e.g. useful/not useful,
     comfortable/concerned with the approach, etc.)

  3. Should the WG use this document as the basis for work on the IP fast
     reroute topic

 Please send your comments by May 9th.

 The document is available at:

 http://www.ietf.org/internet-drafts/draft-atlas-ip-local-protect-00.txt

 The IPR statement is available at:

 http://www.ietf.org/ietf/IPR/avici-ipr-draft-atlas-ip-local-protect.txt

 Abstract from the document:

   This document defines an architecture and selection process for
   providing local protection for IP unicast and/or LDP traffic in the
   event of a single link or node failure until the router has
   converged.  When computing the primary next-hop for a prefix, a
   router S also determines an alternate next-hop which can be used if
   the primary next-hop fails.  The alternate can be either a loop-free
   alternate, which goes to a neighbor whose shortest path to the prefix
   does not go back through the router S, or a U-turn alternate, which
   goes to a neighbor whose primary next-hop to the prefix is the router
   S, and which has itself a loop-free node-protecting alternate, which
   thus does not go through router S to reach the destination prefix.

   A router may indicate the capability to break U-turns on its links;
   only such links can be used as U-turn alternate next-hops.  To signal
   this capability, a router must be capable of detecting when it
   receives traffic for a given destination from a primary neighbor for
   that destination and the router must forward that traffic to the
   selected alternate next-hop.

   To support U-Turn alternates and node-protection, a router must know
   what links its neighbor can consider for alternates, how a neighbor
   will select an alternate, and upon which interfaces a neighbor can
   break U-turns.  This document defines a common selection criteria
   which MUST be followed.  In addition, it is necessary to signal two
   capabilities per link.  First is whether U-turns can be broken on the
   link and second is whether the link can be used as an alternate, as
   determined administratively.

-- 
Alex
http://www.psg.com/~zinin/

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