Re: Waiting State Question

[Kishore Rao <[e-mail]>]

> 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 <[e-mail]>:
> > >
> > > > 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 <[e-mail]>:
> > > > >
> > > > > > 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
> > > > > >
> > > >