Re: Exit-Graceful Restart Condition

[Kishore Rao <[e-mail]>]

----- Original Message ----- 
From: "Padma Pillay-Esnault" <[e-mail]>
To: <[e-mail]>
Sent: Wednesday, May 25, 2005 11:54 AM
Subject: Re: Exit-Graceful Restart Condition


> Kishore Rao wrote:
>
> >----- Original Message ----- 
> >From: "Acee Lindem" <[e-mail]>
> >To: <[e-mail]>
> >Sent: Wednesday, May 25, 2005 10:10 AM
> >Subject: Re: Exit-Graceful Restart Condition
> >
> >
> >
> >
> >>Padma Pillay-Esnault wrote:
> >>
> >>
> >>
> >>>sujay wrote:
> >>>
> >>>
> >>>
> >>>>Hi All,
> >>>>
> >>>>Considering RFC3623, Graceful Restart for OSPF V2 I have a problem;
> >>>>
> >>>>Ex:
> >>>>
> >>>> (network)---- DUT ---- RTA
> >>>>
> >>>>(All in the same area)
> >>>>
> >>>>Assume DUT undergoes a Graceful-Restart, it sends out grace LSA's to
> >>>>RTA and other routers in the 'network'
> >>>>
> >>>>At the instant RTA recvs the Grace-LSA it also goes down.
> >>>>
> >>>>Is there a way in the RFC 3623 specified as to how DUT could Detect
> >>>>this topology change and Exit GR *before* grace period expiry??
> >>>>
> >>>>
> >>>>
> >>>>
> >>>I do not think the RFC covers this case. You are in a double failure
> >>>situation.
> >>>
> >>>I can think of a simple solution. When DUT reacquires its router-lsa.
> >>>It can determine its previous
> >>>neighbors. It can then decide that if within DeadRouterInterval that
> >>>neighbor did not  respond
> >>>to hellos to abort GR. This would be equivalent to the normal
> >>>situation when a router goes down and its
> >>>neigbors takes DeadInterval to bring down their adjacency
> >>>
> >>>
> >>I agree completely with Padma. One point, if RTA comes back up and
> >>originates a new router LSA
> >>then the DUT will detect the inconsistency (as specified in RFC 3623)
> >>with it's pre-restart LSA and
> >>terminate graceful restart.
> >>
> >>
> >
> >Acee,
> >
> >Will this work ?
> >In case there is another router RTB, scan the Hello from RTB for all
> >neighbors on the network and then make sure Hello from RTA has been
received
> >within a Hello interval + 2 (say) . If not, exit GR.
> >
> >
> It is not clear to me. Do you mean that RTB has the same neighbors as
> DUT and is on the same network link ?

Yes.


>
> Padma
>
> >This would be faster than using the reacquired Router and Network LSAs to
> >determine the neighbors, isnt it ?
> >
> >Kishore
> >
> >
> >
> >
> >>
> >>
> >>>Padma.
> >>>
> >>>
> >>>
> >>>>For other routers in the network RTA is still reachable and traffic
> >>>>Will be eventually dropped.
> >>>>
> >>>>Kindly correct me,
> >>>>
> >>>>Regds,
> >>>>Ashok/Sujay
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >
> >
> >