Subject: [Isis-wg] receipt of CSNP's during restart

From: "Matthew Noble" <[email-masked]>
Date: Tue, 16 Apr 2002 14:16:59 +0100

Mike

An interesting point that I think you may need to highlight in the draft.

Say that the restarting node is of type 1/2 and that there are multiple
nodes on a given LAN, and that these other nodes on the LAN are of mixed
type (levels 1, 2 and 1/2). In this case the restarter will in fact receive
2 sets of complete CSNP's over that (LAN) circuit and the T1 timer for that
circuit should not be cancelled until both sets are received (as well as at
least one ACK being received).

However this does lead to the issue of what to do in this circuitstance when
the restarter is type 1/2 but the other nodes on the LAN are only either
level 1 _or_ level 2. May be in that case, although the node is type 1/2,
the circuit should be congfigured as either type 1 or type 2 as appropriate.
In that case the restart knows only to wait for that single CSNP.

Any comments?

Thanks
Matt

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From: Radhika Srivatsa <[email-masked]>
Date: Tue, 16 Apr 2002 09:37:33 -0400 (EDT)

> the circuit should be congfigured as either type 1 or type 2 as appropriate.

Are you saying here that we should take care of the circuit-type
during the configuration phase itself ? If so, what happens when the
topology changes and then the interface would have to receive multi-level
CSNPs ?

thanks

-radhika

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From: "Matthew Noble" <[email-masked]>
Date: Tue, 16 Apr 2002 14:45:21 +0100

Yes that would be a problem - I only suggested setting the level so that if
there were only one type out there on the LAN the restarter wouldn't have to
go through the wait/retry cycles unneccesarily for a set of CNSP's that were
never coming. Possibly another way is when a node ACK's the restart, it
sends the level with the remaining time, so that the restarter can
dynamically work out whether or not to wait for one or both sets of CSNP's.

Thanks
Matt

> -----Original Message-----
> From: Radhika Srivatsa [mailto:[email-masked]]
> Sent: Tuesday, April 16, 2002 2:38 PM
> To: Matthew Noble
> Cc: Mike Shand (E-mail); 'Isis-Wg (E-mail)
> Subject: Re: [Isis-wg] receipt of CSNP's during restart
>
>

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From: mike shand <[email-masked]>
Date: Thu, 18 Apr 2002 10:20:33 +0100

>least one ACK being received).

Yes that is the way it is supposed to work. You are right, this could do 
with clarifying in the text.

>In that case the restart knows only to wait for that single CSNP.

Well, you can certainly tell by looking at the circuit type field of the 
IIHs you receive whether there is a router out there for level1 and one for 
level 2. If there is, you should wait hopefully for the appropriate CSNP. 
If you don't see one, then maybe you could give up rather more quickly. I 
must confess I hadn't thought of trying to optimize that though.

         Mike

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From: Radhika Srivatsa <[email-masked]>
Date: Thu, 18 Apr 2002 15:34:20 -0400 (EDT)

In continuation of this, what about the cancellation of T2 ?
Suppose we have only 2 routers and both of these have only L2 adjacencies
between them (each router is in a different area altho' the interface is
configured for both L1L2) , then the T2 timer for L1 will never get
cancelled as a part of LSPDB synchronization (since there wont be any CSNP
received over the L1 area) and will eventually get cancelled only when the
IETF-restart completes. Is that acceptable ?

Or, we could see if a particular area has any adjacencies within itself
and if there are no adjacencies in that area, then we can cancel T2 for that
area.

Thoughts ?

thanks

-radhika

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From: mike shand <[email-masked]>
Date: Fri, 19 Apr 2002 08:05:12 +0100

>and if there are no adjacencies in that area, then we can cancel T2 for that

If an L1/L2 has no L1 adjacencies, then we can assume that L1 is already 
"synchronized".

         Mike