RE: TE metric and graceful restart

["Naidu, Venkata" <Venkata.Naidu@Marconi.com>]

Yakov,

  Here are my thoughts & comments w.r.t operation of the 
  Traffic Engineering Extensions to OSPF during OSPF 
  Hitless Restart:

  1. First of all, your suggestion might not fit well
     with draft draft-lefaucheur-te-metric-igp-01.txt.
     That is, just changing TE metric might help you to
     stop _some_ unwanted LSPs being setup in restart 
     period but not all. (example, LSPs that use IGP metric 
     in OSPF regular LSAs)
  
  2. If we change any of TE LSA contents and flood the 
     *Restart TE LSAs* to neighbor nodes, then there are 
     2 cases:
	
     (a) The neighbor might have accepted as a helper 
         node
     (b) The neighbor might have rejected (not at
         all received any OSPF-grace LSA etc - for so 
         many reasons I can think of)

   In the case (b), OSPF neighbor will simple flood the restart
   TE LSA into the domain. That is something what you are not
   intended in the below para:
  
   ***
   Neighbors of the restarting node should continue advertise the actual
   unreserved bandwidth on the TE links from the neighbors to that node.
   ***

  3. More over, I think this is a Re-optimization issue rather than
     a restart issue. So, IMHO, it is better not to flood the TE LSA
     (with BW 0 and Infinite Metric changes). 

	- We are expecting that Restart TE LSAs should not be
        flooded beyond neighbor nodes.
	- The new LSPs in the *grace* period will be rejected, or
        cranked back.
      - All those LSPs might take less specific TE path than
        the desired one.
      - If the LSRs are not supporting Adaptivity/Re-optimization
        might end-up with those LSPs hanging around.

  4. Actually, the LSP preventing in the grace period should
     be handled in signaling protocols and definitely not
     using back doors of routing protocols. RSVP and OSPF 
     Restart procedures are independent - one can restart OSPF
     with out letting RSVP going down. 

     So better to exchange the capability in RSVP and prevent
     any LSPs (even of B/W and/or OSPF TE metric are valid)

  5. Minor - it would be better to add/move "Implications 
     on Graceful Restart" section 
     to draft
       draft-ietf-ccamp-gmpls-routing-04.txt
     from draft
       draft-ietf-ccamp-ospf-gmpls-extensions-06.txt

     Because OSPF hitless restart draft is pointing
     to the draft-ietf-ccamp-gmpls-routing-04.txt

--
Venkata.

-> Folks,
-> 
-> It was suggested to set the TE metric to infinity during graceful
-> restart (both for ISIS and OSPF). 
-> 
-> Any objections to this suggestion ???
-> 
-> Yakov.
->