Magnus, thanks for your review. I'm drafting appropriate text for the document considering the interaction between MTU and Block Sizes. When you sad "a small fraction of the MTU" above, i suppose you mean "a large fraction of the MTU", because my understanding would be that fragmentation is much more likely to occur when Block Size is set to (e.g.) MTU / 2 (large fraction) compared to when it was set to (e.g.) MTU / 10 (small fraction).
I'm therefore adding - for Maximal Length Padding: "Depending on the negotiated size, this strategy will commonly exceed the MTU, and then result in a consistent number of fragments reducing delivery probability when datagram based transport (such as UDP) is used." - for Block Length Padding: "The Block Size will interact with the MTU size. Especially for length values that are a large fraction of the MTU, unless the block length is chosen so that a multiple just fits into the MTU, Block Length Padding may cause unneccessary fragmentation for UDP based delivery. Also, chosing a block length larger than the MTU of course forces to always fragment". best, Alex On Wed, Apr 4, 2018 at 11:30 AM, Magnus Westerlund <magnus.westerl...@ericsson.com> wrote: > Reviewer: Magnus Westerlund > Review result: Ready with Issues > > 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. > > _______________________________________________ dns-privacy mailing list dns-privacy@ietf.org https://www.ietf.org/mailman/listinfo/dns-privacy
