Subject: [Isis-wg] draft-ietf-isis-restart-01.txt [continued]

From: "Kent Wong" <[email-masked]>
Date: Tue, 18 Jun 2002 00:40:50 +0000

Hi,

Some more questions on the draft:

4. I don't understand why there is a need for two different timers
T2 and T3. Because when T2 expires/cancels before T3, T3 should be
cancelled anyway. The only case T3 is supposed to be useful is
when T3 expires before T2. The draft states that if T3 expires
before T2, router's own LSP for level which have not completed
their first SPF should be flooded with the OL bit set.

However this assumes that the restarting router has acquired its
own pre-start LSP before T3 expires. What if T3 expires even before
it acquires its pre-start LSP? In that case, it doesn't know what
sequence number it should use in its zero LSP to set the OL bit.
If the seq num it uses is smaller than the seq num in its nbr's DB,
then the zero LSP will be ignored by the helper nbr anyway.

So why not just combine T2 and T3 into a single timer and set the
timer to be the min. remaining holding time of its nbrs. If the timer
expires before it DB re-sync, then graceful restart fails
and everything reverts back to normal. Isn't this much more simpler
and effective?

5. On section 4.3.1.1, the draft mentions the behavior of a router
when it starts for the first time. Does it mean this draft intends to
change the normal ISIS behavior even though it is not a restart?
That means we need to start T2 (but no T1, T3) for each level even
we start for the first time. However, it may not be desirable to set
the OL bit every time ISIS comes up. This should be decided by the
network admin on individual cases whether to set the OL bit or not.

6. Just for clarification, in the draft, it mentions "own" LSP
many times, sometimes it mention own non-pseudonode LSP, sometimes
it mention own LSP including pseudonode. Sometimes, it simply
mention "own" LSP. Should we interpret the "own" LSP as including
pseudonode LSP if it doesn't specify otherwise?

Thanks!

Kent Wong

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