In short, see RFC 2270. Some of the primary differences are that several of the BGP attributes are preserved with confederations, versus that autonomous "look and feel" provided by dedicated ASs, not to mention that any such model would assume that the providers employ confederations as well. Also, managing it would be a nightmare. More importantly though, is that if providers allow customers to maintain sub-ASs of a confederation they're placing a considerable amount of trust in the capabilites of those customers, and errors on the customers part could impact much more than just the customers part. -danny
I'm trying to understand the problem being solved by the Cisco private AS removal feature. In particular, what advantages does it offer over confederations, which would seem to do the same thing when externally advertising customer routes? Is there a performance benefit?
RFC1998-style multihoming with a private AS is a possible application, I suppose, for any routes that are NOT marked with NO-EXPORT.