On Fri, Jun 01, 2012 at 08:03:50PM +0200, Daniel Suchy wrote:
By overwriting origin field, there's no warranty that someone improves performance at all - it's just imagination. In extreme cases, performance can be degraded when someone in the middle plays with origin field and doesn't know reasons, why originating network uses something else than IGP origin. In RFC 2119 words, full implications were not understanded - when this overwriting is done generally.
Uh, what part of "to prevent remote networks from improperly forcing a cold potato routing behavior on you" sounds imaginary?
Also, there must be some historical reason, why origin should not be rewritten (this changed in January 2006). For internal reasons within the network operator still haves enough knobs to enforce own policy (by setting localpref, med on his network).
Not really, no. Not every RFC is 100% correct, and they're often written by people who are not operators (because operators are too busy running real networks :P). Besides, "SHOULD NOT" means "you probably don't want to do this, unless you have a really good reason", and enforcing such an important point in a peering policy is a pretty good reason. You also clearly don't understand the practical use of localpref. When you're trying to implement a simple and relatively common policy like "closest exit routing to a peer with multiple exits", you set the localprefs the same (localpref is usually used to determine WHICH peer you'll be sending to), you set the MEDs the same (if you don't want to artifically select which EXIT to use), AS-PATH lengths are obviously the same if you have multiple exits, and then the next one down is origin code. If you can't reset origin code, you run the risk of a remote network being able to force your network to do something you probably don't want to do (or at least probably wouldn't want to do, if you had any idea what you were doing :P). Please see the previous commentary from Joe Provo, Saku Ytti, etc, they are quite correct. -- Richard A Steenbergen <ras@e-gerbil.net> http://www.e-gerbil.net/ras GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)