Re: Waiting State Question

Erblichs <erblichs@EARTHLINK.NET> Fri, 20 May 2005 03:06 UTC

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Date: Thu, 19 May 2005 19:45:53 -0700
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From: Erblichs <erblichs@EARTHLINK.NET>
Subject: Re: Waiting State Question
To: OSPF@PEACH.EASE.LSOFT.COM
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What is b/n them is broken?

Combine areas and former entry/exit interfaces between
the areas will result in two or more DRs announcements
per pseudonode.

This is taken care of in the Spec? Can anyone find the
section? :-)

Mitchell Erblich
-------------------------

Kishore Rao wrote:
> 
> > Second, "in the case where more than 1 router"
> > is declaring itself as the DR, shouldn't enough
> > time pass (1.5 to 2x) hello interval pass to identify
> > this situation before exiting wait state and
> > poss determine whether 2-ways are forming.  Yes,
> > it could/should exit early, but on that first
> > hello???
> 
> A possible case of A & B declaring themselves as DR would be when comm. b/n
> them is broken; in which case shouldn't router C prefer to elect itself as
> BDR ASAP on receiving the hello from either A or B instead of waiting for a
> longer period of time without the possiblity of neither A or B being elected
> BDR during that time ?
> 
> >
> > Thus, this section of the spec covers the rare simple
> > case where no BDR has yet been elected or is eligible
> > to be elected.
> >
> > Mitchell Erblich
> > -----------------
> >
> >
> >
> > Kishore Rao wrote:
> > >
> > > 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
> > > > > > >
> > > > >