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 revision 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
I-D 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
Request Early review on draft-zhu-intarea-gma by Internet Area Directorate Assigned
Posted at https://mailarchive.ietf.org/arch/msg/int-dir/wFrJRvhiZzVX6kclL1xCRpcHHhE
Reviewed revision 08 (document currently at 14)
Result Not ready
Completed 2021-03-27
review-zhu-intarea-gma-08-intdir-early-pauly-2021-03-27-00
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.