Re: Waiting State Question

Kishore Rao <kishore@IND.ALCATEL.COM> Thu, 19 May 2005 19:31 UTC

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Message-ID: <076701c55ca9$85bbc130$a328fb80@Kishorepc>
Date: Thu, 19 May 2005 13:32:40 -0600
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From: Kishore Rao <kishore@IND.ALCATEL.COM>
Subject: Re: Waiting State Question
To: OSPF@PEACH.EASE.LSOFT.COM
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Right.

> OK. So we agree that an interface comes out of waiting state on receiving
a
> Hello from DR IF that hello does not list any BDR. OTHERWISE an interface
does
> not come out of waiting state on receiving a Hello from DR.
>
>
> Quoting Kishore Rao <kishore@IND.ALCATEL.COM>:
>
> > Not NeighborChange but Backupseen
> >
> > "If the neighbor is both declaring itself to be Designated
> >             Router (Hello Packet's Designated Router field = Neighbor IP
> >             address) and the Backup Designated Router field in the
> >             packet is equal to 0.0.0.0 and the receiving interface is in
> >             state Waiting, the receiving interface's state machine is
> >             scheduled with the event BackupSeen."
> >
> > > I think the NeighborChange events are ignored while an interface is in
> > waiting
> > > state.
> > >
> > > Thanks,
> > > Mukul
> > >
> > >
> > > Quoting Kishore Rao <kishore@IND.ALCATEL.COM>:
> > >
> > > > The question was not about how DR or BDRs are elected. John's
question
> > was
> > > > if the router should exit Wait Timer (and run DR election) on
receving
> > Hello
> > > > from a router declaring itself as DR. Well, from section 10.5 it
should.
> > > >
> > > > Kishore
> > > >
> > > >
> > > > > My guess is that if an interface comes out of the waiting state on
> > > > receiving a
> > > > > Hello from DR (without having received a Hello from BDR), it may
elect
> > > > itself
> > > > > as BDR. This way many routers may elect themselves as BDR. Now all
> > these
> > > > BDR
> > > > > claimants (except one) will ultimately take their claims to
BDRship
> > back
> > > > but in
> > > > > the process each router on the LAN may have to do several DR
> > elections.
> > > > >
> > > > > Here is a paper we wrote recently that may shed further light on
this:
> > > > > http://cs.uwm.edu/~mukul/ospflan.pdf
> > > > >
> > > > > Thanks,
> > > > > Mukul
> > > > >
> > > > > Quoting John Smith <jsmith4112003@YAHOO.CO.UK>:
> > > > >
> > > > > > Hi,
> > > > > >
> > > > > > When a router comes up it starts the Wait Timer before it elects
the
> > > > DR/BDR.
> > > > > > It either
> > > > > > waits for the Wait Timer to expire or it waits for a router
> > declaring
> > > > itself
> > > > > > as the BDR
> > > > > > before it decides that it needs to get out of the 'Waiting'
state
> > (it
> > > > does
> > > > > > this by
> > > > > > generating the Backupseen event).
> > > > > >
> > > > > > My question is why does it wait only for the BDR? Why not the
DR? It
> > can
> > > > when
> > > > > > it recieves
> > > > > > a HELLO from the DR know that their exists a DR and a BDR. Why
not
> > then
> > > > get
> > > > > > out of the
> > > > > > 'Waiting' state?
> > > > > >
> > > > > > Thanks,
> > > > > > John
> > > > > >
> > > > > > Send instant messages to your online friends
> > > > http://uk.messenger.yahoo.com
> > > > > >
> > > >
> >