I am an assigned INT directorate reviewer for <draft-ietf-bess-evpn-irb-extended-mobility>. These comments were written primarily for the benefit of the Internet Area Directors. Document editors and shepherd(s) should treat these comments just like they would treat comments from any other IETF contributors and resolve them along with any other Last Call comments that have been received. For more details on the INT Directorate, see https://datatracker.ietf.org/group/intdir/about/ <https://datatracker.ietf.org/group/intdir/about/>

As with other directorate reviews, I will note that portions of this draft are difficult to read primarily due to the content being very targeted to experts in the EVPN space. The comments below, in my mind, are nits as implementers will be able to fill in the gaps that are addressed in other specifications.

1. The document assumes, without justifying, that the existing sequence number approach is the best way to solve the various mobility scenarios. It is quite possible that other approaches for handling mobility may be more efficient in the long run.

2. I was not able to dig into all of the existing specifications, but I am curious as to why the case of new MAC + new IP doesn't need to be handled. I would assume such a situation in an EVPN should be handled as a new instance of a VM, but wanted to get clarity.

3. RFC 7432 only says that sequence number wrapping needs to be handled, but doesn't specify how it should be handled. With this document redefining assignment of these sequence numbers, I think it would be wise to specify how wrapping should be handled to ensure clear interoperability.

4. Section 6.8 discusses optional ways to speed convergence. There is notional text in there discussing ARP/ND probing. Should there be mention of more explicit techniques such as gratuitous ARP/ND messages from the host? For IPv6, snooping MLD messages of hosts joining the All-Nodes group?