I believe it had to do with multicast datapath (especially link local) being different from the unicast datapath in most routers. Using link local multicast IP addresses may not necessarily guarantee Unicast IP reachability.
When writing 7130 we spent quite a bit of time ensuring that we dont carve out a special data path for the micro-BFD packets. Using link local would have made it a lot simpler. And this is where i think the current proposal is flawed -- they use link local multicast to ensure IP unicast reachability which is incorrect. Cheers, Manav On Thu, Apr 7, 2016 at 11:16 PM, Mach Chen <[email protected]> wrote: > Hi Greg and all, > > > > I just have quick review on the drafts. If my understanding is correct, > the idea is to use multicast destination address other than unicast address > when sending BFD packets over LAG links. And actually this idea has been > proposed in https://tools.ietf.org/html/draft-chen-bfd-interface-00 (the > predecessor of RFC 7130). And at that time, the co-authors of RFC 7130 did > discuss the idea of using multicast destination address, but for some > reason I forget now(I may need to reiterate the discussions on the > archive), the idea was abandoned, although I still think multicast > destination address is a smart idea. > > > > Best regards, > > Mach > ------------------------------ > *From:* Rtg-bfd [[email protected]] on behalf of Gregory Mirsky [ > [email protected]] > *Sent:* Tuesday, April 05, 2016 6:16 > *To:* [email protected]; [email protected] > *Cc:* [email protected]; > [email protected]; [email protected]; Alia Atlas ( > [email protected]) > *Subject:* Two new drafts on (micro-)BFD over MC-LAG interfaces > > Dear All, > > two new drafts, related to RFC 7130, were published before the meeting: > > · BFD on MC-LAG interfaces in IP network > <https://tools.ietf.org/html/draft-tanmir-rtgwg-bfd-mc-lag-ip-00> > > · BFD on MC-LAG interfaces in IP/MPLS network > <https://tools.ietf.org/html/draft-tanmir-rtgwg-bfd-mc-lag-mpls-00> > > > > Greatly appreciate your reviews, comments, questions and suggestions. > > > > Regards, > > Greg >
