This is standard BGP if the IGP metrics are equal. -- Jakob Heitz.
> -----Original Message----- > From: Robert Raszuk [mailto:[email protected]] > Sent: Sunday, March 27, 2011 3:17 PM > To: Jakob Heitz > Cc: [email protected]; IETF IDR > Subject: Re: [GROW] draft-ietf-grow-diverse-bgp-path-dist: > risk of inconsistent path selection > > Jakob, > > > To prevent clients in different clusters from choosing > > different bestpaths based on tie breaker (f): > > Can you restate what is the problem with the above ? > > Today clients would chose different best paths when IGP metric to one > next hop is closest on one to NH1 and closest on the other to > NH2. And > this check happens well above step (f). > > How is this at all related to the diverse path draft like the subject > could indicate ? > > Thx, > R. > > > > > Route selection tie breakers in RFC 4271 state: > > > > f) Remove from consideration all routes other than > the route that > > was advertised by the BGP speaker with the lowest BGP > > Identifier value. > > > > g) Prefer the route received from the lowest peer address. > > > > Suppose RR Planes use different BGP Identifier values. > > If they use the same BGP Identifier, a similar argument > > can be made for peer address. > > > > To prevent clients in different clusters from choosing > > different bestpaths based on tie breaker (f): > > > > The RR Plane that advertises the best path MUST be configured > > with a BGP Identifier higher than that of the RR Plane that > > advertises the 2nd best. This must be higher than that of > > the Plane that advertises the 3rd best and so on. > > > > I'm not sure if this rule completely solves the problem. > > If not, then the "Edge_Discriminator attribute" proposed > > by draft-pmohapat-idr-fast-conn-restore may be required. > > Also, this would need to be applied before rule (f). > > > > -- > > Jakob Heitz. > > > > _______________________________________________ > > GROW mailing list > > [email protected] > > https://www.ietf.org/mailman/listinfo/grow > > > > _______________________________________________ GROW mailing list [email protected] https://www.ietf.org/mailman/listinfo/grow
