I have reviewed this document as part of the Operational directorate's ongoing effort to review all IETF documents being processed by the IESG.  These comments were written with the intent of improving the operational aspects of the IETF drafts. Comments that are not addressed in last call may be included in AD reviews during the IESG review.  Document editors and WG chairs should treat these comments just like any other last call comments.

It's a very detailed document. I do not find any major issue from the OPS point of view, I think this doc is ready for publication as RFC.

Some suggestions and nits:
1. I see a lot of must/MUST used in this documents. I cannot guess your intention. But please check if you have correctly chosen the expression. For example, I think Appendix should be informative, do you really want to use MUST in Appendix A? 

2. In table 1, "store(dest, source)   | Writes source into dest". There is mix of abbreviation and full text. 
I think in the function source->src, in the description dest->destination.

3. In section 5, it's better to have title for the figure. And one arrow(top one) breaks the block. I think this is a nit you should revise.
 
Best,
Tianran