Cogent latency / congestion

Mike Tancsa mike at
Tue Aug 21 01:02:15 UTC 2007

At 05:43 PM 8/20/2007, Steve Gibbard wrote:

>On Mon, 20 Aug 2007, Mike Tancsa wrote:
>>Bell uses Cogent in a large way. The second traceroute was from an 
>>IP in their AS (577) out.   I am prepending out Cogent, but Bell 
>>does everything it can not to use Teleglobe so I am having problems 
>>influencing their routes to come back that way.  They also have a 
>>very odd path out of Chicago.  This is
>Bear in mind that doing "everything they can not to use Teleglobe" 
>probably involves local preference.  Local preference comes before 
>AS path length in the BGP selection order, so nothing you can do 
>with prepending is going to help.

Yes, I realize that.  I think its because they (Bell) pay Teleglobe 
for transit, so they dont want to use it where possible.  Back when I 
signed up with Teleglobe, I was hoping there were some community 
tricks I could use to influence bell's local pref, but because they 
buy transit from Teleglobe, this was not implemented.  I think the 
only thing I could do would be to withdraw the prefixes from Cogent 
or resort to deaggregation so that they would follow a more specific prefix.


>   You'll need to either keep them from seeing the undesirable path 
> at all (drop the announcement, ask your upstreams to limit its 
> propagation, etc.) or convince Bell not to use it.  Depending on 
> the setup, you may be able to limit route propagation with 
> communities, or it may require some phone calls.

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