From: Joe Abley (no email)
Date: Wed Oct 05 2005 - 15:00:51 EDT
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
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