Subject: RE: [Isis-wg] CSNPs in draft-ietf-isis-restart-03.txt

From: Les Ginsberg <[email-masked]>
Date: Fri, 20 Jun 2003 08:19:20 -0700

At 10:45 AM 6/20/2003 -0400, Jeff Parker wrote:
>To return to the example provided.  Let's assume that all three of hannes'
>CSNPs arrive.  Can we conclude that we have a full set?
>
>I don't see any numbering scheme, and I don't see any interlocking scheme
>that would tell us that there is nothing between 1111.1111.1111.00-01 and
>2222.2222.2221.FF-FF (and likewise the gap between 2 and 3.)  How do I know
>that the second CSNP is the second, and not the fifth?

Jeff -

An implementation that interprets 10589 7.3.15.3 as:

If multiple CSNPs are required to make up a complete set AND there are no 
LSPs that fall into the range between (for example) 1111.1111.1111.00-00 - 
1111.1111.1111.ff-ff THEN I can send

CNSP #1 0000.0000.0000.00-00 -> 1111.1111.1111.00-00
CSNP #2 2222.2222.2222.00-00 -> 3333.3333.3333.00-00
etc.

(i.e. never cover the "1111" range in any of the start/end ranges in any of 
the CSNPs)

and say that I have sent a "complete set" , then that implementation is 
non-conforming - or at least "brain-damaged".

It costs an implementation nothing to make sure that the range is covered 
completely i.e. no additional PDUs are required, you simply have to change 
the start ID on the second CSNP to be:

CSNP #2 1111.1111.1111.00-01 -> 3333.3333.3333.00-00

(or extend the end range of CSNP #1).

>One way to make this reliable would be to add an optional "csnp sequence
>number" tlv.  Thus it we have the numbers from 1 to k, and k has an end
>LSPID of all 1s, then we have a complete set.

Given the above, I do not see that this adds any value.

>- jeff parker
>
> > >what would be the "right" mechanism to track down a missing CSNP ?
> > >
> > >i.e. if i send the following CSNPs
> > >
> > >e.g. CNSP #1 0000.0000.0000.00-00 -> 1111.1111.1111.00-00
> > >      CSNP #2 2222.2222.2222.00-00 -> 3333.3333.3333.00-00
> > >      CSNP #3 4444.4444.4444.00-00 -> ffff.ffff.ffff.00-00
>
>Should that read as below?
>          CSNP #3 4444.4444.4444.00-00 -> ffff.ffff.ffff.ff-ff
>
> > >/hannes
>

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---

From: mike shand <[email-masked]>
Date: Fri, 20 Jun 2003 16:32:22 +0100

At 08:19 20/06/2003 -0700, Les Ginsberg wrote:
>(i.e. never cover the "1111" range in any of the start/end ranges in any 
>of the CSNPs)
>

It is certainly seriously broken, since if a neighbor HAS an LSP within the 
range (however small) which was omitted, it will never be triggered to 
re-transmit it. Thats why 10589 says a "complete" range and defines what it 
is. There is no room for slapdashness here.

         Mike