Last Call Review of draft-ietf-dprive-padding-policy-04

Request Review of draft-ietf-dprive-padding-policy
Requested rev. no specific revision (document currently at 06)
Type Last Call Review
Team Transport Area Review Team (tsvart)
Deadline 2018-04-04
Requested 2018-04-04
Requested by Magnus Westerlund
Authors Alexander Mayrhofer
Draft last updated 2018-04-04
Completed 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 Last Call review of -04 by Magnus Westerlund (diff)
Tsvart Telechat review of -05 by Magnus Westerlund (diff)
Assignment Reviewer Magnus Westerlund
State Completed
Review review-ietf-dprive-padding-policy-04-tsvart-lc-westerlund-2018-04-04
Reviewed rev. 04 (document currently at 06)
Review result Ready with Issues
Review completed: 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.