Acee,

> Padma,
>
> I don't think it simplifies the helper code (or specification)
> to apply the grace LSA to all neighbor instances of restarting
> router. Here are my reasons:
>
> 1. Conceptually, I don't think it is right to apply the link
> local grace LSA to neighbors that are not on the link.

Let's be more precise - we are talking about adjacencies of the restarting
router. A grace lsa from router X is received by router Y who has n
adjacencies to router X. One grace lsa should apply to the n adjacencies.

I beg to differ. Conceptually, the grace lsa is used to signal that
a *router* is restarting to its neighbors. The only reason, why we use
a link-local lsa is that we have *no* other way to just prevent the lsa
from being flooded further by these neighbors.

I need to stress again that event being processed is a *router* restart
*not* a link restart.

Why the need to process that the router X is restarting n times ?
By analogy, if one gets 10 copies this email should one answer
it 10 times ? ;-)

> 2. There are simply more corner cases -
>
> - When you receive a second grace LSA from the restarting
> router, do you update the reason and grace period for
> all neighbor instances or only ones on that segment?
>

The second and consequent ones grace lsas are acknowledged but I do not
update the grace period/reason for the simple reason that the restarting
router (planned or unplanned) do not change those parameters on the fly.

> - When do exit helper mode? Is it when the first grace
> LSA is withdrawn or all the grace LSAs? I certainly don't
> think there should be disconnect between entering and
> exiting helper mode.

The first maxaged grace lsa will cause the helper to exit.

>
> I do agree that it is somewhat more robust for the case where
> you are adjacent with the same router on more than one link.
> However, I don't see this as a real big gain. Has anyone
> else implemented this draft?

The big gain ?

I think that we expose ourselves to more timing dependencies corner cases
by considering a grace lsa per link processing on the helper side.

This unnecessary added complexity (per interface) will simply not scale.

Thanks

Padma

>
> Thanks,
> Acee
>
>
>
> Padma Pillay-Esnault wrote:
>
> > Rajesh
> >
> >
> > Rajesh Varadarajan wrote:
> >
> >>Acee, Padma,
> >>
> >
> > <snip>
> >
> >>>>>>I do think it simplifies things if a restarting router originates the grace LSAs
> >>>>>>on all it's interfaces (or at least all with full neighbor
> >>>>>>
> >
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >
> >>>>>>
> >>>>>>adjacencies if it a planned restart).
> >>>>>>
> >
> >>>>>>
> >>>>>>
> >>>>>>
> >>
> >>The above statement seems to imply (my reading) that a restarting router
> >>
> >>can only send Grace LSA's out of some (not all) of its interfaces. The
> >>
> > It doesn't imply that - clearly we send to all our neighbors.
> >
> > Padma
> >
> >>
> >>spec however requires the router to send the grace-lsa out of all
> >>interfaces on which it has full neigbhors. Failure to do so would always
> >>result in its helper mode being terminated by others.
> >>
> > <snip>
> >
> >>>>>I also agree with you .. that's what I do - the restarting router sends
> >>>>>grace lsa over all interfaces. But from a Helping router perspective
> >>>>>we should do as in 00-txt. It simplifies the helper code.
> >>>>>It also prevents corner cases where we might not help all adjacencies
> >>>>>(when we should).
> >>>>>
> >>>>>Padma
> >>>>>
> >>>>
> >>>>I haven't heard anyone object to why the 00-txt.
> >>>>
> >>>
> >>>I will - I specifically agree with
> >>>
> >>>
> >>>
> >>> Note that Router Y only needs to receive a single grace-LSA from
> >>> X, even if X and Y attach to multiple common segments.
> >>>
> >>>I don't like using an LSA with link local scope to enter/terminate
> >>>helper mode for neighbors on different interfaces. It is better if the
> >>>link local grace LSA only applies to that link.
> >>>
> >>
> >>Given the behavior above, I think the each neighbor should be considered
> >>independently on a segment by segment basis.
> >>
> >>
> >>thanks,
> >>rajesh
> >>
> >>
> >
>
>
> --
> Acee
>

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