RE: Route update stats

[Guy Davies <]

[..snip..]

>     Karsten,
>     
>     thats really an interesting question:
>     
>     ACOnet receives a full routing-table from SPRINT/AS1239 and from
>     GEANT/AS20965.  Comparing the current BGP session counters:
>     
>     neighbor SPRINT, uptime ~20weeks, Received  7926940 messages
>     neighbor GEANT,  uptime ~ 7weeks, Received 29597194 messages 
>     
>     which gives a long-term average of 
>     
>     	419 BGP update messages per minute from GEANT but only
> 	 39 BGP update messages per minute from SPRINT
> 	 
>     afaik GEANT does no BGP flap damping, SPRINT however 
> does, according to
>     http://www.sprint.net/policy/bgpdamp.html
>     
>     I don't know if damping is the only reason for the factor 
> >10 between
>     them, there might be other reasons as well, e.g. SPRINT 
> backbone is
>     Cisco based, GEANT is Juniper based and they might be 
> using completely
>     different IGPs and iBGP concepts.

It could also be due to the fact that SPRINT certainly constrains (or used
to constrain) the maximum prefix length it will accept (not longer than /24
- used to be /18 I think but that was way too restrictive).  Don't know
about GEANT?  Logically, you'd expect smaller blocks to be flapped more than
larger aggregates so removing the smaller blocks entirely from what you
accept/announce would reduce the number of announcements/withdrawls you make
(even taking flap damping into account).

It might be worth looking at the relative size of the "full" routing tables
you receive from SPRINT and GEANT.  If it's more from GEANT, that might be
the answer.

Regards,

Guy
---
Guy Davies          Telindus
IP Architect        Hatchwood Place, Farnham Road, Odiham, Hants, RG29 1AB

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