Re: [Idr] comments on draft-ietf-idr-rs-bfd

Robert Raszuk <robert@raszuk.net> Tue, 01 August 2017 18:38 UTC

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From: Robert Raszuk <robert@raszuk.net>
Date: Tue, 01 Aug 2017 20:38:41 +0200
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To: Job Snijders <job@ntt.net>
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Subject: Re: [Idr] comments on draft-ietf-idr-rs-bfd
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Hi Job,

Indeed intentions of authors of this draft in this respect would be very
useful.

I think the notion was that if few clients report that they can not reach Z
then it means that Z is down for all other clients.

So if A, B tell RS that Z is down that could trigger declaring Z as
unreachable for all especially if C does not even support the new SAFI.

The other interesting question is if Z is the only next hop for a prefix P
for a client does it get withdrawn or is left as the only resort to reach P
?

Thx,
R.


On Tue, Aug 1, 2017 at 8:32 PM, Job Snijders <job@ntt.net> wrote:

> Hi Robert,
>
> On Tue, Aug 01, 2017 at 04:50:27PM +0200, Robert Raszuk wrote:
> > Not quite ... Nick is correct - next hop reachability are global in
> > RS.  Sure each client may have his path in his view but this is not
> > what will limit the next hop liveness decision.
> >
> > See messages and suggestions from John on how to treat failures
> > reported by N clients as something more important then failures of NH
> > reachability reported by one or two clients. In both cases they would
> > affect entire RS not only those clients views.
>
> This surprises me. If clients A & B report that they can't reach Z, that
> doesn't imply anything about whether C can reach Z. In such a scenario
> would be somewhat counter-intuitive if the RS prunes all paths with
> next-hop Z from C's Loc-RIB, based on a message from client A or B.
>
> I think I would benefit from further elaboration on what the draft's
> intentions are in this regard.
>
> Kind regards,
>
> Job
>