Telechat Review of draft-ietf-bess-evpn-irb-extended-mobility-18
review-ietf-bess-evpn-irb-extended-mobility-18-intdir-telechat-haberman-2024-11-22-00

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?