[Int-dir] Intdir early review of draft-zhu-intarea-gma-08

[Tommy Pauly via Datatracker <[e-mail]>]

Reviewer: Tommy Pauly
Review result: Not Ready

I am an assigned INT directorate reviewer for draft-zhu-intarea-gma. 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/>.

This document does propose several mechanisms that can increase the MTU
efficiency of encapsulation protocols in the style of GRE, which seems useful.
However, the document needs to be improved for clarity and safety before
publication even in the Independent stream, in my opinion.

- Some claims in the abstract and introduction need explanation. A device
connected to multiple networks doesn’t directly require solutions like GRE that
use additional encapsulation; many devices connect without this. Instead, this
solution really is isolated to overlays across networks. This needs to be
clarified for scope early on.

- The GRE references are to an Independent submission of Huawei’s version of
GRE. It seems misleading to not be referencing RFC 2784 or RFC 2890 directly.

- Section 4 should be broken into multiple sections, one for each format; it is
difficult to understand where the details for each mode overlap or contrast.

- Many of the reference to IP headers seem to assume IPv4 (such as the IP
checksum, not present in IPv6). Any document coming out now should be designed
with IPv6 in mind first, and I would suggest breaking out the examples for both
IPv6 and IPv4 separately. Similarly, any UDP encapsulation mode needs to be
given as a complete example, not just an aside.

- Section 5, on fragmentation, may run into some of the problems with fragments
in general. Please see RFC 8900. The recommendation is to either remove the
fragmentation support, or strongly discourage it and reference RFC 8900.

- Similarly, concatenation as described in Section 6 may be better handled at
higher layers. QUIC, for example, allows packing multiple packets in single UDP
datagrams.