Telechat Review of draft-ietf-core-new-block-11

Request Review of draft-ietf-core-new-block
Requested rev. no specific revision (document currently at 11)
Type Telechat Review
Team Internet of Things Directorate (iotdir)
Deadline 2021-05-04
Requested 2021-04-28
Requested by Éric Vyncke
Authors Mohamed Boucadair, Jon Shallow
Draft last updated 2021-05-03
Completed reviews Genart Last Call review of -10 by Pete Resnick (diff)
Tsvart Last Call review of -11 by Colin Perkins
Iotdir Telechat review of -11 by Emmanuel Baccelli
Possibly my last request for a IoT directorate review :-O
But, let's have a review on this one but from someone not working in the CORE WG

Thank you

Assignment Reviewer Emmanuel Baccelli 
State Completed
Review review-ietf-core-new-block-11-iotdir-telechat-baccelli-2021-05-03
Posted at
Reviewed rev. 11
Review result Ready with Nits
Review completed: 2021-05-03


iotdir telechat review of draft-ietf-core-new-block-11
Emmanuel Baccelli, 3 May 2021


Many thanks for this document. In general, the spec is well written as far as I could see. 
I have a few nits and suggestions (see below).

My main question is about the use of Confirmable messages. Maybe I missed something, but it seems to me the use of CON messages is not recommended in the spec, but is nevertheless evoked in the spec. Is there room for  simplification, or is it considered too "radical" to only specify the use of Q-Block with non-confirmable messages?

Details below.

Best regards,



# Section 1

## Second to last sentence: 
"such a recommendation does not work with a flooded pipe DDoS situation." 
=> an explicit ref would feel natural at this point of the text (RFC8782 again? Or another ref?).

## Last sentence:
Ends a little dry. How about completing it with something similar to:
OLD: "This document introduces the CoAP Q-Block1 and Q-Block2 Options (Section 3)"
NEW: "This document introduces the CoAP Q-Block1 and Q-Block2 Options which allow block-wise transfer to work with series of Non-confirmable messages, instead of lock-stepping using CON messages".

# Section 3
It would read more naturally to my eyes if you'd swap around the section's content in the beginning (part before 3.1 begins) like this:
 - move up the overview of the Q-Block options, i.e essentially the part "Q-Block1 and Q-Block2 Options are designed to work in particular with NON requests and responses..." and onwards;
 - gather afterwards the bullet points summing up the advantages / limitations /drawbacks of Q-Block options compared to the Block options.

# Section 4.1
the first time you mention POST, PUT? FETCH, iPATCH etc., I suggest you explicitly cite RFC8132 again.

# Section 4.3, for Response code 4.13
"If a server receives payloads with different Request-Tags for the same resource, it should continue to process all the bodies as it has no way of determining which is the latest version, or which body, if any, the client is terminating the transmission for."
=> since this is a *should* and not a MUST, would it make sense to add reassuring an implementer note on how to comply while minimzing buffer memory requirements?
Are there use cases where the server is *very* constrained in RAM for instance (say: Class 1 devices in RFC 7228)?

# Section 7.1
Do I understand correctly that this configuration (all confirmable messages for a given body) is *not* recommended?
The statement "it is expected that all requests and responses using Q-Block1 and Q-Block2 will be Non-confirmable" is confusing at first sight, it begs the question: why specify the configuration using CON, then?
But maybe I missed something.

# Section 11
If the Request-tag happens to be an outer option (or if there is a proxy) does the above comment on section 4.3 (response code 4.13) translate in a potential resource exhaustion vulnerability for the server?