Subject: [Isis-wg] ISIS graceful restart...

From: "Jeelani Syed" <[email-masked]>
Date: Tue, 20 Apr 2004 14:14:38 -0400

Hi,

From  draft-ietf-isis-restart-05.txt, section 3.3.1( Adjacency reacquisition during restart )
it says.

   "Once the timer T3 has expired or been cancelled, subsequent IIHs are 
    transmitted according to the normal algorithms, but including the 
    restart TLV with both RR and RA clear."

I am wondering why restart router needs to wait untill T3 expires to send IIH with RA and RA cleared.
Can it be done once T1 expires? If not why?

Thanx,

-jeelani.sm

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From: Les Ginsberg <[email-masked]>
Date: Tue, 20 Apr 2004 11:50:35 -0700

>Can it be done once T1 expires? If not why?

You are correct. This looks like a typo (one that has had a long life). The 
text should say "T1".
Thanx for spotting this.

Note that the state table in 4.2 is correct in this regard.

    Les

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From: mike shand <[email-masked]>
Date: Tue, 20 Apr 2004 19:58:27 +0100

>Can it be done once T1 expires? If not why?

T3 has expired OR BEEN CANCELLED

You don't need to wait until T3 expires.

         Mike

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From: mike shand <[email-masked]>
Date: Wed, 21 Apr 2004 07:41:17 +0100

My apologies Jeelandi, I thought you were simply questioning whether you 
had to wait for timer expiry, as opposed to cancelling. But you are right, 
this should be when T1 is cancelled. This is actually a remnant of the 
original design where we didn't want to refresh the adjacency until we were 
sure that the restart recovery was complete. But that changed a while ago, 
and somehow this piece of text was not changed accordingly, but, as Les 
pointed out, the state table was.

We should fix this.

         Mike

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From: Les Ginsberg <[email-masked]>
Date: Wed, 21 Apr 2004 08:26:58 -0700

At 07:41 AM 4/21/2004 +0100, mike shand wrote:
>original design where we didn't want to refresh the adjacency until we 
>were sure that the restart recovery was complete. But that changed a while 
>ago, and somehow this piece of text was not changed accordingly, but, as 
>Les pointed out, the state table was.
>
>We should fix this.
>
>         Mike

Here is the change proposed by Mike and myself to address this issue:

Section 3.3.1 "Adjacency reacquisition during restart", page 10, para 2:

Current text:

"Once the timer T3 has expired or been cancelled, subsequent IIHs are..."

Revised text:

"Once the timer T1 has been cancelled, subsequent IIHs are ..."

Explanation:

The difference is more than a typo. At one point in time (long, long ago) 
the reference to T3 was probably appropriate. And since T3 never gets 
restarted, it either expires or is cancelled. T1 however, can run a locally 
configurable number of times (as explained later in the same section) and 
it is only on the cancellation of the timer that resumption of normal IIHs 
should be sent.

If this revision is acceptable, Alex has agreed to try to get this into the 
doc before the RFC is published.

    Les