Jeff, Thank you very much for your clear clarification of the BGP Loc-Rib! I will look into RFC4271 again to understand this point.
Thanks, Shunwan -----Original Message----- From: Jeffrey Haas [mailto:jh...@pfrc.org] Sent: Friday, October 12, 2018 10:06 PM To: Zhuangshunwan <zhuangshun...@huawei.com> Cc: Tim Evens (tievens) <tiev...@cisco.com>; grow@ietf.org Subject: Re: [GROW] bmp loc-rib monitoring scope question (was Re: I-D Action: draft-ietf-grow-bmp-local-rib-02.txt) Shunwan, On Fri, Oct 12, 2018 at 12:16:39AM +0000, Zhuangshunwan wrote: > > From: GROW [mailto:grow-boun...@ietf.org] On Behalf Of Jeffrey Haas > > [Trimming original thread to re-ask my core question.] > > > > On Thu, Oct 11, 2018 at 09:18:17PM +0000, Tim Evens (tievens) wrote: > > > The local RIB in BMP should only contain what is/would be used/installed. > > > > >From where? BGP's best route? The routing table's active route? > > > > > In other words, the local rib sent via BMP should not contain the > > > suppressed prefixes that were not installed due to another routing > > > protocol/direct/static having a better preference. > > > > Which ties into the RFC question about where other protocols are injected > > into the Decision Process. > > > > If you read the RFC as literally saying it's injecting it into the Decision > > Process (section 9.4), the LocRib should be the best route and thus the > > active route regardless of whether it was learned from BGP or not. > > [Shunwan] IMO, the LocRib should include selected and used routes. We can > consider some concrete examples. > Example 1: > If a router enable six parallel load balancing, and now there are 8 available > candidate routes for one destination D. > In this case, there will be 6 routes of the same destination D exist in the > Loc-RIB, but only one of them is the best route. Loc-Rib in the RFC 4271 sense only covers selecting the best route, singular. The fact that your FIB implementation may balance over that for ECMP purposes is an implementation detail. > Example 2: > If we enable BGP Fast Reroute (FRR) in a router, then there may exist a best > route and a backup/alternate route in BGP for one destination D. > In this case, there will be 2 routes of the same destination D exist in the > Loc-RIB, but only one of them is the best route. Again, Loc-Rib in the RFC 4271 sense would consider only the best route. The implementation is using the contents of the Adj-Rib-In to select additional information for local forwarding purposes. I.e. similar to the ECMP case above. -- Jeff _______________________________________________ GROW mailing list GROW@ietf.org https://www.ietf.org/mailman/listinfo/grow
