Subject: [OSPF] question on strict LSA checking in ospf graceful restart

From: "Sunil Patro" <[email-masked]>
Date: Sun, 25 Jun 2006 15:38:04 -0700

RFC 3623 mentions that - 

RestartHelperStrictLSAChecking

      Indicates whether or not an OSPF restart helper should terminate
      graceful restart when there is a change to an LSA that would be
      flooded to the restarting router or when there is a changed LSA on
      the restarting router's retransmission list when graceful restart
      is initiated.  The suggested default is enabled.

I am curious as regards to what is the need of this option.

Thanks
Sunil

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From: Acee Lindem <[email-masked]>
Date: Mon, 26 Jun 2006 08:42:31 -0400

Hi Sunil,

>I am curious as regards to what is the need of this option.
Do you mean the behavior or the option to enable/disable it? If the network
topology is changing during a graceful restart, there may be routing 
loops and
termination when changes occur is one way to decrease the likelihood. 
However,
in most cases graceful restart proceeds very quickly and the preferred 
deployment
is to disable early termination. The default of "enabled" has been in 
the draft since
its inception and I did not change it when I took over as editor. Both 
of the
implementations with which I'm familiar default this parameter to 
"enabled".

Hope this helps,
Acee

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From: Acee Lindem <[email-masked]>
Date: Mon, 26 Jun 2006 12:48:12 -0400

Answered too quickly on a Monday morning - See inline.

> implementations with which I'm familiar default this parameter to 

I meant default to "disabled". Refer to http://www.ietf.org/rfc/rfc4167.txt
Note that the Cisco implementation was not available at the time this 
RFC was
written. It also defaults to "disabled".

Thanks,
Acee