Early Review of draft-zhu-intarea-gma-08
review-zhu-intarea-gma-08-intdir-early-pauly-2021-03-27-00

Request Review of draft-zhu-intarea-gma-08
Requested rev. 08 (document currently at 14)
Type Early Review
Team Internet Area Directorate (intdir)
Deadline 2021-04-19
Requested 2021-03-19
Requested by Adrian Farrel
Authors Jing Zhu, Satish Kanugovi
Draft last updated 2021-03-27
Completed reviews Intdir Early review of -08 by Tommy Pauly (diff)
Comments
This document has been presented for publication on the Independent Submissions Stream.
At this stage, I am not looking for the reviewer to say whether the document describes a good idea, but I am interest in the reviewer's opinion of:
- Would publication of this document harm any existing IETF work?
- Is the document clear enough to be implemented?
- Are there any technical flaws that would lead an implementation to fail?

Please note that the re-use of port 114 has been discussed at length with the ADs and with IANA. The conclusion is that it can be re-used provided that this document includes a comment warning deployers about the small chance of a collision.
Assignment Reviewer Tommy Pauly 
State Completed
Review review-zhu-intarea-gma-08-intdir-early-pauly-2021-03-27
Posted at https://mailarchive.ietf.org/arch/msg/int-dir/wFrJRvhiZzVX6kclL1xCRpcHHhE
Reviewed rev. 08 (document currently at 14)
Review result Not Ready
Review completed: 2021-03-27

Review
review-zhu-intarea-gma-08-intdir-early-pauly-2021-03-27

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.