Last Call Review of draft-ietf-tsvwg-aqm-dualq-coupled-24
review-ietf-tsvwg-aqm-dualq-coupled-24-opsdir-lc-jiang-2022-08-26-00

Reviewer: Sheng Jiang
Review result: Has Issues
Document: draft-ietf-tsvwg-aqm-dualq-coupled-24
Review Date: 2022-08-26

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 experimental document defines a framework for coupling the AQM algorithms
in two queues intended for flows with different responses to congestion. It is
the network part of the L4S architecture that enables both very low queuing
latency and high throughput at the same time.

I have concerns on the operational description in this document. This document
claims its mechanims can be deployed in the current network. But it lacks the
description on how and why it can works back-compatibly. I heard there were
intensive debate regarding to the usage of ECT (I did not participate it
myself), but the document has not introduced the reason or background why it is
allowed to use ECT from the urgement.

Another minor comments, there is another reason that can cause the result
mentioned in 4.2: if irresponsible terminals labels classic ect(0) flows into
l4s ect(1), it would overload l4s queue.

Regards,

Sheng