Last Call Review of draft-ietf-dprive-padding-policy-04
review-ietf-dprive-padding-policy-04-tsvart-lc-westerlund-2018-04-04-00

Request Review of draft-ietf-dprive-padding-policy
Requested rev. no specific revision (document currently at 05)
Type Last Call Review
Team Transport Area Review Team (tsvart)
Deadline 2018-04-04
Requested 2018-04-04
Requested by Magnus Westerlund
Other Reviews Secdir Last Call review of -04 by Charlie Kaufman (diff)
Genart Last Call review of -04 by Meral Shirazipour (diff)
Opsdir Last Call review of -04 by Joe Clarke (diff)
Tsvart Telechat review of -05 by Magnus Westerlund
Review State Completed
Reviewer Magnus Westerlund
Review review-ietf-dprive-padding-policy-04-tsvart-lc-westerlund-2018-04-04
Posted at https://mailarchive.ietf.org/arch/msg/tsv-art/zcm8B_A9yB9gQh8QuzGFa-qrTas
Reviewed rev. 04 (document currently at 05)
Review result Ready with Issues
Draft last updated 2018-04-04
Review completed: 2018-04-04

Review
review-ietf-dprive-padding-policy-04-tsvart-lc-westerlund-2018-04-04

I have reviewed this document as part of TSV-ART task to review documents with potential transport related issues. 

I note that the document in its final recommendation regarding block sizes do consider MTU for reasonable size choices. What I am missing in Section 4 is the discussion of MTU as impacting this. From my perspective, it appears reasonable to:
In Section 4.1 consider if the Block Size will interact with the MTU. Especially for block sizes that are a small fraction of the MTU, unless the block is chosen so that a multiple just fits the MTU, the block padding may cause unnecessary fragmentation for UDP based delivery. Also chosing a block size larger than the MTU of course forces one to always fragment. 

In Section 4.2 I think depending on the negotiated size, the downside is that it will commonly result in a consistent number of fragments reducing delivery probability. I haven't digged into the negotiation part about maximum response size. But, I assume that this is not necessarily chose based on MTU constraints, but other limitations in the system. 

Note that these comments only applies for datagram based transport without its own fragmentation mechanism, e.g. UDP.