Cogent/Level 3 depeering

Wed Oct 5 19:00:51 UTC 2005

On 5-Oct-2005, at 13:43, Jeff Shultz wrote:

> And why isn't this apparently happening automatically? Pardon the  
> density of my brain matter here, but I thought that was what BGP  
> was all about?
>
> I welcome any education the group wishes to drop on me in this matter.

For most ISPs, normal practice is to advertise your own routes and  
those of your customers to your peers, and to your transit providers.  
To your customers, you advertise everything. If someone decides to  
stop peering with you, you reach them through one or more of your  
transit providers.

A relatively small number of providers are transit-free -- that is,  
they rely solely on customer and peering connections to reach the  
entire Internet.

When a transit-free ISP loses a peer, there is no transit path to  
fall back on.

While it's undoubtedly true that there are third parties who  
interconnect and peer with both cogent and layer(3), the fact that  
those are peering connections and not customer/transit connections  
means that the third parties are unlikely to advertise cogent routes  
to layer(3), and vice versa.

This is a money issue. ISPs don't generally give away transit for free.

Joe