Re: Graceful Restart

[Acee Lindem <[e-mail]>]

John, Krishna,

John has it pretty much right but there is one additional key
point. If the restarting router doesn't succeed its role as
DR on interfaces where it was previously DR the specification
is broken. The restarting router uses his own pre-restart
router and network LSAs to determine when graceful restart
has converged. A DR election would change the topology and
the restarting router would detect an LSA inconsistency and
exit graceful restart prematurely.

Thanks,
Acee

John Smith wrote:
> Krishna,
> my 2 euros (dollars are out !!!)
>
>
>>draft-ietf-ospf-hitless-restart-07.txt:
>>2.  Operation of restarting router:
>>
>>Point 2) If the restarting router determines that it was
>>Designated
>>          Router on a given segment immediately prior to the
>>restart,
>>          it elects itself as Designated Router again
>>
>>Q1)Why does this need to be done while restarting?
>>    AND
>>    How does it help ??
>
>
> Its helps in maintaining sanity in the network. Others think that this router is still up
> and continue trusting him as DR. When he comes up he should not break this trust and
> should ideally start operating as a DR.
>
> The basic concept is that if he resigns from DRship then the BDR will take over and they
> will need to again re-elect the BDR .. which is a messy affair. The whole point of
> graceful restart is to avoid such events !!
>
>
>>Q2)What if normal DR/BDR election takes place "on exiting
>>    graceful restart"
>
>
> Why do you want to land in this mess? You will again need to re-issue your LSAs, etc.
> Everybody will have to re-synch .. and the whole purpose of graceful restart will be
> defeated.
>
> Others more informed about this protocol can correct me whatever i missed out!
>
> JS
>
>
>
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--
Acee