Re: OSPF and ISIS SequenceNumber

It may just be that designers thought that this would never happen,
so adding a procedure to handle it was going to increase the proto
complexity w/o any real added advantage ?

IS-IS does throtle LSP generation by default to 5 seconds, the spec
says less than 30 per sec.
2^32 * 5 secs is a lot of time for your net to be running :)
(~700 years of continuos flapping :)

OSPF does have that too BTW, but it does not seem to be protocol
specified but added implementation by cisco et. al.

-Carlos

Bit Gossip @ 10/04/2010 3:13 -0300 dixit:
> Experts, can you help me understand the following.....
>
> OSPF from 'routing TCP/IP vol I pag 455':
> "If the present sequence number is MaxSequenceNumber and a new instance
> of the LSA must be created, the router must first flush the old LSA from
> all databases. This is done by setting the age of the existing LSA no
> MaxAge (defined later in this section) and reflooding it over all
> adjacencies."
>
> ISIS from 'routing TCP/IP vol I pag 611':
> "If the Sequence Number increments to the maximum (0xFFFFFFFF), the
> IS-IS process must shut down for at least 21 minutes (MaxAge +
> ZeroAgeLifetime) to allow the old LSPs to age out of all databases."
>
> IS-IS implements as-well a procedure to purge LSPs by setting the
> RemainingLifetime to 0; so why does it use such a dramatic measure of
> shutting down instead of purging the troubled LSP as OSPF does?
>
> Thanks,
> bit.
>
>
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-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net