Justin W. Newton writes:
Another drawback to this model is that if you peer with people at one
exchange and one exchange only you would only give them routes that are
within the local region, and not all of your routes. This may be a problem.
It may not.
It would be. What happens if one of your connections to a peering
point goes down? You can't fall back to go through another peering
point because they are not sending you the routes there. The way to
do it is probably with either AS padding or BGP communities. I've
never played with them, but Enke Chen from MCI wrote a draft on the
subject which he spoke about at the last NANOG.
Alec