Subject: Graceful restart helper question

From: Sanjay BM <[email-masked]>
Date: Mon, 15 Nov 2004 18:32:12 +0530

Hi,

Please see the following lines from the graceful restart rfc.

=-=-=-=-=-=-=-=-
RFC3623
Section 3.1 "Entering Helper Mode"
Page 8:
If Y was already helping X on the associated network segment, the new
grace-LSA should be accepted and the grace period should be updated
accordingly.
=-=-=-=-=-=-=-=-

I had few questions relating to these lines.

1. Why should a helper accept new grace LSAs?

2. Should the helper reset its grace-period timer to the grace-period
value received in this new grace LSA?

3. What should happen if the local policy on the helper had accepted
the grace-period value of the earlier received grace LSA and hence
entered helper mode, but now the policy rejects the grace-period value
set in the new grace LSA? Should the behavior in this case be
implementation specific? The policies could reject other parameters
for that matter, ex: grace-restart-reason.

Kindly let me know.

Thanx,
Sanjay

---

From: Acee Lindem <[email-masked]>
Date: Mon, 22 Nov 2004 17:12:27 -0500

Hi Sanjay,

Sanjay BM wrote:

>---------- Forwarded message ----------
>From: Sanjay BM <[email-masked]>
>Date: Mon, 15 Nov 2004 18:32:12 +0530
>Subject: Graceful restart helper question
>To: [email-masked]
>
>
>Hi,
>
It is to handle the case where the OSPF routing software
wants override an existing grace LSA (e.g., if it restarts more
than once while preserving the data plane). It is the responsibility
of the restarting router to assure this capability is not
abused.

Note that this was originally discussed as far back
as the 01 version of the draft. However, there was not much discussion
then as to why the override option was selected.

http://peach.ease.lsoft.com/scripts/wa.exe?A2=ind0112&L=ospf&P=R96&I=-3

>value received in this new grace LSA?
Yes.

>for that matter, ex: grace-restart-reason.
The RFC doesn't specify how local policies are handled. Hence it is an
implementation decision. However, my opinion would be to apply the
policy terminate the graceful restart since the latest grace LSA was
rejected.