FWIW, IMO reordering and resquencing are synonymous. I would not expect readers to track the difference, even if coined as different in this document.
I would encourage “misordering” as a more reliably interpreted term for changing the order of packets from their arrival. Also note: reordering and resequencing both could mean EITHER “putting things in the correct order” or “putting things back to the order in which they arrived” (which may not be correct). Delay is added whenever EITHER type of reordering/resequencing occurs - or (notably) when misordering occurs in the first place. Another type of delay that midpoint nodes should not try to correct is jitter, i.e., variation in the arrival of a packet stream. Again, any attempt to change the arrival pattern necessarily introduces delay - as does anything that increases that variation. I.e., the doc focuses on situations where the endpoint could allow packets to arrive out of order, but that’s not the only reason to avoid resequencing. Joe > On Aug 3, 2026, at 4:51 PM, Greg White > <[email protected]> wrote: > > Hi Joe, > > Thanks for the detailed feedback, this is very helpful. We will try to tackle > as many of these suggestions as we can in the next version. > > For clarity, in the draft we defined the terms “reordering” = making packet > out of order, “resequencing” = putting them back in order. To help avoid > confusion, I’ve edited your points to align with this terminology - with > square brackets where I’ve made a change. > > On your final point that it isn’t clear that this document is saying anything > different from RFC3819: yes, the two excerpts you quoted aren’t markedly > different, and Section 1 paragraph 2 > <https://www.ietf.org/archive/id/draft-white-intarea-reordering-04.html#section-1-2> > indicates that the main issue with RFC3819 isn’t that statement, it is the > text that follows. Also, I think we’ll end up with more concrete > recommendations than what are in the draft currently. > > -Greg > > > From: Joe Touch <[email protected] <mailto:[email protected]>> > Date: Monday, August 3, 2026 at 8:42 AM > To: Greg White <[email protected] <mailto:[email protected]>> > Cc: Internet Area <[email protected] <mailto:[email protected]>>, > "[email protected] <mailto:[email protected]>" <[email protected] > <mailto:[email protected]>>, "[email protected] <mailto:[email protected]>" > <[email protected] <mailto:[email protected]>> > Subject: Re: [IPsec] New Version Notification for > draft-white-intarea-reordering-04.txt > > Hi, all, > > Although the new and updated information provided in this document could be > useful, it’s not clear that this document supersedes any of the advice > provided in RFC 3819. > > Additionally, it omits key information as to why layer 2 frame ordering is > maintained in certain protocols. > > In particular: > - the abstract describes that [resequencing] “can introduce delays that > result in net degradation of performance”. Those delays can also be > irrelevant, e.g., if no further [resequencing] occurs and the receiver > [resequences] anyway (as with TCP). The lack of such [resequencing] can also > increase work at the receiver, as when TCP sends SACK rather than cumulative > ACK. I.e., the impact is not always clear. > > - on-path interpretation of TCP streams, including DPI, don’t always react as > well as modern TCP endpoints > > - the impact on fragmentation and reassembly is not addressed sufficiently; > the discussion should cite the primary requirements (791, 8200) and go into a > bit more detail. > > - IPsec is clearly sensitive to reordering. Most protocols, TCP included, can > adapt to some level of reordering only up to a limit. Not only are there > limits, but (as noted above) there is a cost at the receiver to support these > capabilities. This doesn’t appear to be addressed. > > - there are MANY variations to TCP as deployed, as well as other protocols. > Implementations with compromised resources, such as in IoT or low-power > devices, may not all be up to “modern” standards. > > - there are protocols that require ordering at L2 (ATM being the primary > example); it is useful to reiterate that this document isn’t recommending a > change that would violate other L2 semantics that depend on ordering. > > AFAICT, the only clear requirements here are: > >> Subnetwork implementers SHOULD avoid introducing unnecessary packet >> reordering. However, where packet reordering is an unavoidable consequence >> of mechanisms that improve overall performance or reliability (for example, >> packet striping across multiple links or link-layer retransmissions), the >> resulting packet reordering SHOULD generally be exposed to the receiving >> endpoint rather than hidden by subnetwork resequencing. >> > RFC3819 says: > > This suggests that subnetwork implementers should try to avoid packet > reordering whenever possible, but not if doing so compromises > efficiency, impairs reliability, or increases average packet delay. > > It isn’t clear that this document is saying anything different from RFC3819. > > It may be useful as informational, but as presented it isn’t clear it should > be a BCP; at best, it is an informative update to the context in which > RFC3819 recommendations remain valid. > > Joe > > >> On Jul 7, 2026, at 9:19 AM, Greg White >> <[email protected] >> <mailto:[email protected]>> wrote: >> >> FYI >> >> On 7/6/26, 5:25 PM, "[email protected] >> <mailto:[email protected]> <mailto:[email protected]>" >> <[email protected] <mailto:[email protected]> >> <mailto:[email protected]>> wrote: >> >> >> A new version of Internet-Draft draft-white-intarea-reordering-04.txt has >> been >> successfully submitted by Greg White and posted to the >> IETF repository. >> >> >> Name: draft-white-intarea-reordering >> Revision: 04 >> Title: Proposal for Updates to Guidance on Packet Reordering >> Date: 2026-07-06 >> Group: Individual Submission >> Pages: 12 >> URL: https://www.ietf.org/archive/id/draft-white-intarea-reordering-04.txt >> <https://www.ietf.org/archive/id/draft-white-intarea-reordering-04.txt> >> Status: https://datatracker.ietf.org/doc/draft-white-intarea-reordering/ >> <https://datatracker.ietf.org/doc/draft-white-intarea-reordering/> >> HTML: https://www.ietf.org/archive/id/draft-white-intarea-reordering-04.html >> <https://www.ietf.org/archive/id/draft-white-intarea-reordering-04.html> >> HTMLized: >> https://datatracker.ietf.org/doc/html/draft-white-intarea-reordering >> <https://datatracker.ietf.org/doc/html/draft-white-intarea-reordering> >> Diff: >> https://author-tools.ietf.org/iddiff?url2=draft-white-intarea-reordering-04 >> <https://author-tools.ietf.org/iddiff?url2=draft-white-intarea-reordering-04> >> >> >> Abstract: >> >> >> Several link technology standards mandate that equipment guarantee >> in-order delivery of layer 2 frames, apparently due to a belief that >> this is required by higher layer protocols. To meet this requirement >> they implement a "resequencing" operation to restore the original >> packet order. This can introduce delays that result in net >> degradation of performance. Modern TCP and QUIC implementations >> support features that significantly improve their tolerance to out- >> of-order delivery. This draft is intended to provide new information >> for layer 2 technology standards regarding the need to assure in- >> order delivery to support IETF protocols. >> >> >> >> >> >> >> The IETF Secretariat >> >> >> >> >> >> >> >> _______________________________________________ >> IPsec mailing list -- [email protected] <mailto:[email protected]> >> To unsubscribe send an email to [email protected] >> <mailto:[email protected]> > > _______________________________________________ > IPsec mailing list -- [email protected] <mailto:[email protected]> > To unsubscribe send an email to [email protected] > <mailto:[email protected]>
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