Jeff, RR does not change BGP next hop on the update. N1 and N2 can determine P-tunnel neighbor based on BGP next hop.
Lucy -----Original Message----- From: Jeffrey (Zhaohui) Zhang [mailto:[email protected]] Sent: Wednesday, September 23, 2015 9:36 AM To: Lucy yong; Eric Rosen; [email protected] Cc: [email protected] Subject: RE: [bess] comment on draft-ietf-bess-ir Lucy, Perhaps you can elaborate the following then? There is no BGP session between N1/N2 and N3. RR does not understand "upstream/downstream" neighbor. Even on N1/N2/N3, upstream/downstream are wrt different flows. How do you configure such policies? > > [Lucy] If each BGP session keeps track of P-tunnel neighbor state: > > 1) the downstream neighbor, 2) the upstream neighbor, or 3) N/A. A > > simple policy can suppress a lot distribution: redistribute a Leaf > > A-D route if and only if it is sent by a downstream neighbor. This > > ensures that ingress PE receives all the Leaf A-D routes from all the > > egress PEs. Jeffrey > -----Original Message----- > From: Lucy yong [mailto:[email protected]] > Sent: Wednesday, September 23, 2015 10:31 AM > To: Jeffrey (Zhaohui) Zhang <[email protected]>; Eric Rosen > <[email protected]>; [email protected] > Cc: [email protected] > Subject: RE: [bess] comment on draft-ietf-bess-ir > > Hi Jeff, > > As I said before, RR always need to distribute Leaf A-D routes. > > Lucy > > -----Original Message----- > From: Jeffrey (Zhaohui) Zhang [mailto:[email protected]] > Sent: Wednesday, September 23, 2015 9:28 AM > To: Lucy yong; Eric Rosen; [email protected] > Cc: [email protected] > Subject: RE: [bess] comment on draft-ietf-bess-ir > > Lucy, > > The point is that we rely on BGP distribution mechanism, and we cannot > expect RRs to do more than basic route distribution. > > Jeffrey > > > -----Original Message----- > > From: Lucy yong [mailto:[email protected]] > > Sent: Wednesday, September 23, 2015 10:26 AM > > To: Jeffrey (Zhaohui) Zhang <[email protected]>; Eric Rosen > > <[email protected]>; [email protected] > > Cc: [email protected] > > Subject: RE: [bess] comment on draft-ietf-bess-ir > > > > Hi Jeff, > > > > We seem across each other. Two potential optimizations I proposed: > > 1) suppress unnecessary redistribution; 2) method for child to > > change its patent. I am not clear which one example illustrates. > > Both need to work with and without RR. > > > > -----Original Message----- > > From: Jeffrey (Zhaohui) Zhang [mailto:[email protected]] > > Sent: Wednesday, September 23, 2015 9:17 AM > > To: Lucy yong; Eric Rosen; [email protected] > > Cc: [email protected] > > Subject: RE: [bess] comment on draft-ietf-bess-ir > > > > Lucy, > > > > Let's use this example to illustrate the points we tried to get through: > > > > N1 N2 > > \ / > > \ / > > RR > > | > > | > > N3 > > > > > > N3 originates a Leaf AD route. Originally the parent is N1 so the > > Leaf AD route has RT(N1). Then the parent changes to N2 so N3 sends > > an update with new RT(N2). There is no withdraw from N3 at all. > > > > The route and its update is sent by N3 to only the RR. > > > > If Constraint Route Distribution (RFC 4684) is used, only N1 will > > get the initial route, and when N3 sends the update, RR will > > withdraw it from N1 and send the route to N2. > > > > If that is not used, then both N1 and N2 will get the original route > > and the update. Because the RT(N2) in the update does not match N1, > > N1 will treat the update as an implicit withdraw. > > > > So, in the first case, N1 will get the withdraw that is controlled > > by the RR, which only follows BGP route distribution process and > > does not understand MVPN/IR rules at all. In the second case, there > > is no explicit withdraw at all. In both cases, N3 only sends an update. > > > > Jeffrey > > > > > > > -----Original Message----- > > > From: Lucy yong [mailto:[email protected]] > > > Sent: Wednesday, September 23, 2015 9:58 AM > > > To: Eric Rosen <[email protected]>; Jeffrey (Zhaohui) Zhang > > > <[email protected]>; [email protected] > > > Cc: [email protected] > > > Subject: RE: [bess] comment on draft-ietf-bess-ir > > > > > > Hi Eric, > > > > > > When non-segmented ingress replication is used, the ingress PE > > > needs to see the Leaf A-D routes from all the egress PEs. (The > > > ingress PE is the upstream parent in this case, even if the > > > ingress PE is not a BGP peer of the egress PEs.) This means that > > > the RT on the Leaf A-D routes needs to identify the ingress PE. > > > However, the Leaf A-D routes may need to travel over multiple BGP > > > sessions before they reach the > > ingress PE. > > > Some of these BGP sessions may be IBGP sessions, some may be EBGP > > sessions. > > > It's rather important that the route not get discarded before it > > > reaches the ingress PE, even though it passes through multiple BGP > > > speakers. If one wants to constrain the distribution of the > > > routes, one still has to guarantee that the routes will reach their > > > targets. > > > > > > > > > [Lucy] If each BGP session keeps track of P-tunnel neighbor state: > > > 1) the downstream neighbor, 2) the upstream neighbor, or 3) N/A. A > > > simple policy can suppress a lot distribution: redistribute a Leaf > > > A-D route if and only if it is sent by a downstream neighbor. This > > > ensures that ingress PE receives all the Leaf A-D routes from all > > > the > egress PEs. > > > > > > Thanks, > > > Lucy > > > > > > _______________________________________________ BESS mailing list [email protected] https://www.ietf.org/mailman/listinfo/bess
