RE: Question about IS-IS Restart Signaling

Jeff -

I think Sandip's point is of significance. In order for the scenario you
raise to be relevant here you have to have some routers in which the
forwarding plane is protected by UPS but the control plane is not -
while other routers are fully protected (or otherwise isolated from the
power failure).

Nevertheless, I agree that the scenario raised by Ramesh needs to be
considered - and to the extent your example suggests ways in which it
might occur - however unlikely - that is helpful.

   Les

> -----Original Message-----
> From: Parker, Jeff [mailto:jeffp <at> middlebury.edu]
> Sent: Sunday, March 26, 2006 11:28 AM
> To: Sandip Devnath (sadevnat); Les Ginsberg (ginsberg); Kandula,
Ramesh;
> isis-wg <at> ietf.org
> Subject: RE: [Isis-wg] Question about IS-IS Restart Signaling
> 
> I don't think this is a case we should alter the design for.
> I can imagine a scenario where some routers are on a UPS, and others
are
> not.
> 
> Again, this is an existence proof that the problem can happen, not
> something we need to engineer for.
> 
> - jdp
> 
> ________________________________
> 
> From: Sandip Devnath (sadevnat) [mailto:sadevnat <at> cisco.com]
> Sent: Sun 3/26/2006 12:46 PM
> To: Parker, Jeff; Les Ginsberg (ginsberg); Kandula, Ramesh; isis-
> wg <at> ietf.org
> Subject: RE: [Isis-wg] Question about IS-IS Restart Signaling
> 
> 
> 
> Wouldn't it cause whole forwarding to go away? Graceful restart's
> requirement is to have the forwarding intact, while routing protocol
> restarts (across different cards or same card).
> 
> Regards
> Sandip
> 
> -----Original Message-----
> From: Parker, Jeff [mailto:jeffp <at> middlebury.edu]
> Sent: Saturday, March 25, 2006 4:40 AM
> To: Les Ginsberg (ginsberg); Kandula, Ramesh; isis-wg <at> ietf.org
> Subject: RE: [Isis-wg] Question about IS-IS Restart Signaling
> 
> I would think that losing power in a building and recovering might
well
> give you several routers rebooting at once.
> 
> - jeff parker
> 
> ________________________________
> 
> From: Les Ginsberg (ginsberg) [mailto:ginsberg <at> cisco.com]
> Sent: Sat 3/25/2006 3:02 AM
> To: Kandula, Ramesh; isis-wg <at> ietf.org
> Subject: RE: [Isis-wg] Question about IS-IS Restart Signaling
> 
> 
> 
> Hmmm...an interesting question.
> 
> I would have to say that the RFC is not explicit on this point.
> 
> >From an interoperability standpoint, I would be concerned that
> implementations might not parse past the initial restart TLV and
> therefore might not process a second restart TLV. This would not be
> fatal as the restarting router would eventually retransmit an IIH-RR
> (presumably by this time the other restarting router would have seen
its
> RA) - but would be suboptimal as it would delay the reestablishment of
> the adjacency on the part of the restarting router. On the other hand,
> it would provide a means of decreasing the total number of IIH-RAs
sent
> in response to the IIH-RRs in such a case.
> 
> This is, of course, a very unlikely case for two reasons:
> 
> 1)It is unlikely that two routers would restart "at the same time"
> 2)As the requirement on sending the IIH-RA is to send it "immediately"
> (with jitter on the LAN) the interval between receipt of IIH-RR from
two
> different routers would need to be quite small.
> 
> In the conservative spirit of being "strict in what you send" I would
be
> inclined to NOT include multiple restart TLVs in the same IIH. I would
> recommend sending two IIHs one immediately after the other. Note that
> such short bursts are already allowed in the case of LSP/CSNP
> transmissions.
> 
>    Les
> 
> 
> > -----Original Message-----
> > From: Kandula, Ramesh [mailto:Ramesh.Kandula <at> SpirentCom.COM]
> > Sent: Friday, March 24, 2006 11:07 PM
> > To: 'isis-wg <at> ietf.org'
> > Subject: [Isis-wg] Question about IS-IS Restart Signaling
> >
> > Hi all,
> >
> > According to RFC 3847, if multiple routers on a broadcast network
> restart
> > around the same time, is the helper (receiving) router supposed to
> include
> > multiple instances of Restart TLVs with RA bit set (one for each
> > restarting
> > router) in it's hellos?
> >
> > thanks
> > ramesh
> >
> > _______________________________________________
> > Isis-wg mailing list
> > Isis-wg <at> ietf.org
> > https://www1.ietf.org/mailman/listinfo/isis-wg
> 
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> 
> 
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