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Comments draft-ietf-mpls-recovery-frmwork-00.txt

  • From: Porotsky Sergey <Sergey.Porotsky@ecitele.com>
  • Date: Thu, 5 Oct 2000 14:09:13 +0300
  • Cc: alchiu@att.com, bcain@baynetworks.com, Ben.Mack-Crane@tellabs.com, Changcheng.Huang@sce.carleton.ca, fiffi@nortelnetworks.com, jamoussi@nortelnetworks.com, jonweil@nortelnetworks.com, ken.owens@tellabs.com, loa.andersson@nortelnetworks.com, scivanlar@coreon.net, Srinivas.Makam@tellabs.com

Title: RE: Comments draft-ietf-mpls-recovery-frmwork-00.txt

    [Porotsky Sergey]  Vishal Hi, and thanks for your answer. See my comments below. Regards, Sergey.

    [Vishal]
    I mentioned the FIS as one possibility to intimate the affected
    source(s) of a
    failure that requires their intervention. It does not mean that the
    source(s) will
    begin recovery immediately on receipt of the message. They will, as you
    observe,
    take care of planned rerouting before initiating reroute recovery. In
    fact for
    the reroute recovery to be reliable, they would have to wait for the
    routing tables
    to converge. (Otherwise, an alternate route picked by the source might
    need to be
    changed again once the tables converge.)

    As regards the explosion of the RNT tables, that would depend on the
    number and
    granularity of the LSPs in the network. In fact, that is why, our
    assumption
    was that re-route recovery works in conjunction with IP routing
    protocols, and
    has to wait for them to converge. In that case, no special notification
    to
    the sources is needed. They learn all they need to via the routing
    updates.

    The RSVP Tear-Down message itself may not reach the desired source, if
    the
    routing tables haven't converged, so I am not sure that that would be a
    useful way to intimate the source. (Note that the FIS message uses
    a preconfigured reverse path, that does not depend on L3 routing
    tables.)

    [Porotsky Sergey]  OK. You are correct, for re-routing based on  IP/OSPF routing protocol it isn't necessary to use both FIS and Tear-Down. But why do you want to use IP routing and don't use Explicit Path Selection for re-rerouting? I think, that for pre-planned re-routing we MUST to use Explicit Route (pre-defined before failure) and also for on-demand re-rerouting we SHOULD use Explicit Routing - at least for Traffic Engineering Goals.