Re: Cogent/Level 3 depeering

[Richard A Steenbergen <ras () e-gerbil net>]

On Wed, Oct 05, 2005 at 01:41:50PM -0400, Todd Vierling wrote:
> On Wed, 5 Oct 2005, Matthew Crocker wrote:
>
> > > I'm curious where in your contract you think Cogent guaranteed you
> > > connectivity to Level 3?
> >
> > My original contract was with NTT/Verio which Cogent purchased last year when
> > Verio nuked their Boston POP.   I'm having the contract dug out of the
> > archives to look at what it says.  IMHO  I pay Cogent for Transit to the whole
> > Internet,  If I wanted partial transit or local peering I would order/contract
> > and pay for that.   Cogent is not currently providing me full transit service.
> > I really don't care who pulled the plug, it is Cogents job to fix it for me as
> > I am their customer.
>
> "Isn't BGP supposed to work around this sort of thing?"
>
> This comes down to a little more than just "depeering" -- at least in the
> BGP sense.  There's active route filtering going on as well if connectivity
> is dead; after all, I can bet the house that at least one of Cogent's
> network edge peers has connectivity to Level3, and vice versa.

No there really isn't.

> So perhaps the question you should be asking is:  Why didn't routes for
> these networks fall over to the other upstream peers which *are* capable of
> moving the packets?  Surely MCI, AT&T, Sprint, and others would carry the
> packets to the right place.  I can see the paths right here....

Cogent does not buy transit from MCI, AT&T, or Sprint.
Level 3 does not buy transit from MCI, AT&T, or Sprint.

You can only be a "tier 1" and maintain global reachability if you peer 
with every other tier 1. Level 3 is obviously the real thing, and Cogent 
is "close enough" (at least in their own minds :P) that they won't buy 
real transit, only spot routes for the few things that they are missing 
(ATDN and Sprint basically). There is no route "filtering" going on, only 
the lack of full propagation due to transit purchasing decisions, or in 
this case the lack thereof.

-- 
Richard A Steenbergen <ras () e-gerbil net>       http://www.e-gerbil.net/ras
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