[c-nsp] NSF aware OSPF

[Volodymyr Yakovenko]

On Thu, Sep 09, 2004 at 12:19:42PM -0700, Siva Valliappan wrote:
>> Hello!
>>
>>  According to SSO/NSF documentation in case of OSPF usage neighboring routers
>>  should be "NSF-aware".
>>
>>  It looks like that for some equipment (like Cisco Catalyst 3550) IOS with
>>  NSF-awareness functionality will not be ever available. It looks like there
>>  is no any General Deployment NSF-aware IOS available.
>>
>
>as long as the C3550 ships off the 12.1E codebase there will be no support
>for NSF-awareness for that platform.  please contact your account team
>for future software roadmap plans for the C3550.

Tnx for the point.

>>  In case of ISIS there is 'Cisco configuration option' which brakes "all
>>  routers in subnet should ne NSF-aware for NSF switchover" rule.
>>
>
>i fail to understand your question here.  there is only 1 IETF standard
>for ISIS based graceful restart / awareness (unlike OSPF), so there should
>be no interoperability issues as far as graceful restart awareness is
>concerned.  however, for graceful restart capable devices like the
>C12000, C10000, C6500 / C7600, C7500, C7300, we can operate in 2 modes
>while using ISIS.  in one mode we make use of the standard ISIS
>graceful restart mechanism.  now this is a "graceful" restart.  we
>notify routing peers on a failover and continue forwarding on the old
>forwarding table till the new routing table is rebuilt.  in the other
>mode, we can actually failover in a "stateful" manner.  this is the
>Cisco proprietary extension.  when failing over in a "stateful"
>manner we do internal checkpointing of the ISIS topology, peer information,
>etc.  we are therefore able to handle a failover in a manner that is
>transparent to the rest of the network.  the other ISIS peers will
>not know when a failover occurs as we do not do any special
>signalling, etc (everything is handled internally).

Tnx for deep description.

>so in neither of the above cases should other routers in a subnet
>fail.  so can you please shed more light?  (unless i misunderstood the
>question).

There is a "stateful" proprietary implementation of ISIS switchover, which 
does not require a "graceful" capabilities on ISIS peers.

Will similar functionality be available for OSPF "stateful" switchover? 

>>  Does anyone know will such "Cisco" mode be available for OSPF or not?
>
>in the case of OSPF there were 2 different IETF drafts for graceful
>restart support.  Cisco implemented one, Juniper the other.  so Cisco
>and Juniper do not interwork for OSPF based graceful restart currently.

Ok, but there is "stateful" mode for ISIS, which does not require from peer 
router "graceful" capabilities. It is good to have same functionlity for OSPF,
I believe.

-- 
Regards,
Volodymyr.