Re: Exit-Graceful Restart Condition

[Acee Lindem <[e-mail]>]

sujay wrote:

>Hi Padma,
>
>Guess we *must* run the dead interval timer on a per neighbor basis,
>  
>
Hi Sujay,

IMHO, this is the norm rather than the exception.

>else
> for the maximum configured dead interval amongst all possible
>neighbours.
>It could be of course implementation specific.
>
>Solves more than the one issue mentioned in this thread !
>
>Regds,
>Sujay
>
>-----Original Message-----
>From: Mailing List [mailto:[e-mail]] On Behalf Of Padma
>Pillay-Esnault
>Sent: Friday, May 27, 2005 8:40 PM
>To: [e-mail]
>Subject: Re: Exit-Graceful Restart Condition
>
>
>Kishore Rao wrote:
>
>  
>
>>----- 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.
>> 
>>
>>    
>>
>
>This is not a solution that you can rely one. For one - you can only use
>
>it on a BCAST interface where there are
>2+ neighbors possible. It will not work for p2p for example.
>
>I prefer a generic solution.
>
>Padma
>
>  
>
>> 
>>
>>    
>>
>>>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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>           
>>>>>>>
>>>>>>>              
>>>>>>>
>>>>     
>>>>
>>>>        
>>>>
>> 
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