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.

This draft introduces an SCHC Compound ACK message, which is intended to reduce the number of SCHC ACKs in the ACK-on-Error mode.

From the operation point of view, there are several concerns.
1. What's the interaction with legacy devices? I.e., what if the sender does not support the Compound ACK message?
2. Combining several ACKs to one Compound ACK will introduce more response delay(no?). What's the impact to the sender? For example, more buffer/cache for re-sending messages. For example, the setting of timer expiration, etc.

I do not think these are big issues, but I hope there are texts to clarify in the document.