From be4cd99a3688cef19f66e1c8b8e0506ffc1e13fc Mon Sep 17 00:00:00 2001 From: Ondrej Zajicek Date: Thu, 22 Dec 2011 13:20:29 +0100 Subject: Implements deterministic MED handling. Thanks to Alexander V. Chernikov for many suggestions. --- doc/bird.sgml | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'doc') diff --git a/doc/bird.sgml b/doc/bird.sgml index 7f53f02..b8dabf4 100644 --- a/doc/bird.sgml +++ b/doc/bird.sgml @@ -1316,6 +1316,21 @@ for each neighbor using the following configuration parameters: received from the same AS (which is the standard behavior). Default: off. + deterministic med BGP route selection + algorithm is often viewed as a comparison between individual + routes (e.g. if a new route appears and is better than the + current best one, it is chosen as the new best one). But the + proper route selection, as specified by RFC 4271, cannot be + fully implemented in that way. The problem is mainly in + handling the MED attribute. BIRD, by default, uses an + simplification based on individual route comparison, which in + some cases may lead to temporally dependent behavior (i.e. the + selection is dependent on the order in which routes appeared). + This option enables a different (and slower) algorithm + implementing proper RFC 4271 route selection, which is + deterministic. Alternative way how to get deterministic + behavior is to use igp metric Enable comparison of internal distances to boundary routers during best route selection. Default: on. -- cgit v1.2.3