Hi Zenon, On Thu, Oct 29, 2009 at 10:09:16AM +0200, Zenon Mousmoulas wrote:
> BGP RIB lookups. However, for traffic flowing from sources behind > that path (inbound for us), how would one go about doing just that? > > [ ... ] > > This is quite similar in concept to the mechanics of calculating the > source peer AS: an RPF lookup would be required again, which should > return the AS-path instead of the next-hop. Of course once again we > have the assumption that routing is symmetric, which however in > internet environments is far from the truth, but it's still better > than nothing. How difficult would it be to implement this so that we > could have a src_as_path aggregation primitive? Implementing a trivial src_as_path is quick and easy ... but is that any useful? It's something non-deterministic and it's also not always possible to infer whether it's correct or pure rubbish. When i posed myself that question some time ago, i thought that even if a trivial implementation takes just a couple of hours, bottom line it's time wasted. I guess on a topic like "src_as_path" there is margin for a study, some research or at least some ample discussion maybe bringing in further interested people (coming from the NREN world, you perhaps can think of somebody at this propo?) with the goal of coming up with something clever. Recently, for example, having spoken to somebody on similar topics i started wondering if further information about ingress traffic is better inferred from the network itself (say: BGP, NetFlow, TTL values, etc.), from out-of-band data (say: AS macros, RIPE data, etc.) which would be all part of a map or a mix of the two. Cheers, Paolo _______________________________________________ pmacct-discussion mailing list http://www.pmacct.net/#mailinglists
