Re: Reposting on ccamp: Clarification on RSVP Restart Procedure

[Anca Zamfir <ancaz@cisco.com>]

Lou,
At 12:28 PM 10/16/2002 -0400, Lou Berger wrote:
> At 08:46 AM 10/16/2002, Anca Zamfir wrote:
>
>
>
> > >Hi,
> > >I have a couple of questions regarding the RSVP restart procedure:
> > >
> > >In draft-ietf-mpls-generalized-rsvp-te-07.txt, section 9.5.2. "Procedures
> > >for the Restarting node", one of its paragraph reads:
> > >"In the special case where a restarting node also has a resta(r)ting
> > >downstream neighbor, a Recovery_Label object should be used instead of a
> > >Suggested_Label object."
> > >
> > >This implies that the restarting node - N1 is able to detect that its
> > >downstream neighbor -
> correct.
>
> >  N2 has also restarted, that is N1, N2 is the
> > >restarting order.
> > >
> > >For the LSPs established from N2 to N1,
>
>
> > since N2 cannot detect that N1 has
> > >restarted, N2 will send Path messages using the Suggested Label.
> This statement is incorrect. Please reread section 9.5.2 second paragraph.
I reread the paragraph you mention from section 9.5.2 (Procedures for the 
Restarting node):

"If the forwarding state was preserved, then the node initiates the
   state recovery process.  The period during which a node is prepared
   to support the recovery process is referred to as the Recovery
   Period.  The total duration of the Recovery Period is advertised by
   the recovering node in the Recovery Time parameter of the Restart_Cap
   object.  The Recovery Time MUST be set to the duration of the
   Recovery Period in all Hello messages sent during the Recovery
   Period.  State that is not resynchronized during the Recovery Period
   SHOULD be removed at the end of the Period."

Could you please clarify why my statement is incorrect?

If N1, N2 is the restarting order and if N2 cannot detect that N1 has 
restarted then N2 will send Path with Suggested Label to N1 according to 
8-th paragraph in the same section.

Do you say that there is a way for N2 to know that N1 has restarted?



> > >In this case N1 will not be able to differentiate the case where this
> > >message is a new Path message sent with Suggested Label or a Path message
> > >for an old LSP for which recovery happens. Is N1 expected to handle the
> > >two cases in the same way? If yes, why was the Recovery Label "invented"
> > >and why wasn't the Suggested Label considered good for the RSVP restart
> > >procedure?
> > >
> Please refer to section 9.5.2.  It clearly states what N1 is to do in this 
> case.
It is clear what to do for the LSP established from N1 to N2 but not for 
the LSPs established from N2 to N1. Again, I may be missing something, any 
clarification would be appreciated.

Thanks,
Anca


> Lou
>
> > >Thanks,
> > >Anca