Jeff Wheeler writes:
On Thu, Dec 15, 2011 at 1:07 AM, Keegan Holley <keegan.holley@sungard.com> wrote:
Had in interesting conversation with a transit AS on behalf of a customer where I found out they are using communities to raise the local preference
That sounds like a disreputable practice.
While not quite as obvious, some large transit ASes, like Level3, reset the origin to I (best) sometime between when they learn it and when they announce it to their customers and peers. This similarly causes them to suck in a bit more traffic than they might otherwise.
Once upon a time, UUNET did the opposite by setting origin to unknown for peer routes, in an attempt to prefer customer routes over peer routes. We moved to local preference shortly thereafter as it became clear this was "changing" the routes in some meaningful way; if a customer was multihomed to us and another provider, this might affect path selection. (The original thought was that local pref might be too heavyweight, but of course later it became the standard.) Joe