Hi Eric, Please see below.
-----Original Message----- From: Eric C Rosen [mailto:ero...@juniper.net] Sent: Tuesday, September 01, 2015 3:15 PM To: Lucy yong; Jeffrey (Zhaohui) Zhang; draft-ietf-bess...@tools.ietf.org Cc: bess@ietf.org Subject: Re: [bess] comment on draft-ietf-bess-ir > However, a child can use one leaf A-D with the new parent with a new > label and later send withdraw leaf A-D to the old parent Lucy, Note that "both" of Leaf A-D routes you mention above have the same NLRI and the same next hop. Thus to BGP, these are really the same route. What you are suggesting is: - Send a route with a particular set of attributes to one neighbor; - Send the same route with a different set of attributes to another neighbor; - Then withdraw the route from the first neighbor without withdrawing it from the second. This sort of functionality is not really supported by the BGP distribution mechanisms. The MVPN mechanisms generally assume the typical BGP distribution mechanisms, where BGP chooses the bestpath for a particular NLRI, and then distributes it. [Lucy] What you say is that, in BGP distribution mechanism, BGP (child here) chooses the bestpath (i.e. parent here) for a particular NLRI, then distributes the NLRI to all BGP peers (including the parent node). Since the NLRI is only stored by the parent node and may be removed by old parent node, such distribution mechanism has no advance for such purpose and causes a scaling issue. To reduce the distribution symptom, it should explicitly require that, if a node receiving a leaf A-D route is not the parent node including old parent node, the node should not redistribute the leaf A-D route; in other words, only the parent node is allowed to readvertise the leaf A-D route. In fact, for this purpose, use REFRESH msg may be better than UPDATE. This is about mcast membership announcement. One question, if one ASBR or ABR node that is the parent for a set of downstream neighbors fails, what is the procedure for the downstream neighbors to select a new parent? If a child fails, the parent should update multicast state as if the child is withdrawn. Thanks, Lucy Eric _______________________________________________ BESS mailing list BESS@ietf.org https://www.ietf.org/mailman/listinfo/bess
