Re: [sidr] BGPSEC Threat Model ID

[Brian Dickson <[e-mail]>]

On Sat, Nov 5, 2011 at 12:21 AM, Jakob Heitz <[e-mail]> wrote:
> On Nov 4, 2011, at 3:41 PM, "Brian Dickson" <[e-mail]> wrote:
>
>> Once a route crosses a peer connection or goes "downhill", it can no
>> longer go "uphill"
>> or cross another peering link.
>
> Why can it not cross a peering link?
>
> --
> Jakob Heitz.

When two networks peer, they agree to exchange routes for their
respective customers.

If A announces a route to B, that route is A's customer and _not_ B's customer.
So, by the nature of the agreements, B cannot announce that route to
another peer, C.

Take the worst case - a tier-1 network. All their routes are either
customer routes, or peer routes.
If they were to send their peers' routes to their peers, they would be
sending all routes to everyone.
They would be providing transit, for free, to their peers. This would
not be good for many reasons.

Put another way - when network B sends routes to peer C, it is
providing transit to those routes.
It generally only wants to do that for customers, especially if that
happens to be its primary business.

Brian