Fred and WG participants, I have finally freed up some cycles to read draft-templin-6man-parcels2-14 <https://datatracker.ietf.org/doc/html/draft-templin-6man-parcels2-14>, and I have found some issues with it that need to be addressed with respect to its handling of UDP.
The big one -- if I have correctly understood what I have read -- is that it's possible for a single parcel of a parcellated UDP packet to be turned into a stand-alone UDP packet (see Section 7.1 <https://datatracker.ietf.org/doc/html/draft-templin-6man-parcels2#name-packetization-over-non-parc>) and delivered to an end system as such (see Section 7.4 <https://datatracker.ietf.org/doc/html/draft-templin-6man-parcels2#name-final-destination-restorati>). That packet would contain a Parcel Parameters UDP Option to tell the endpoint host that the packet is a parcel and not a complete UDP datagram, but the option kind is taken from the SAFE option space (KIND = 127; see draft-ietf-tsvwg-udp-options#section-10 <https://datatracker.ietf.org/doc/html/draft-ietf-tsvwg-udp-options#section-10>). Legacy endpoints that do not understand UDP options will ignore that SAFE option and will deliver the parcel as if it were a complete UDP datagram. That, to my mind, is completely unacceptable. Unlike TCP, which is a byte-stream protocol in which segment boundaries have no meaning for the upper layer, UDP is a datagram protocol in which message boundaries are meaningful to the upper layer. The protocol has a contract with the upper layer to deliver a message as it was submitted or not at all. Delivering a parcel in a manner that can be misinterpreted as a complete datagram violates that contract. It is possible to repair this defect by making the Parcel Parameters Option, or something with equivalent functionality, into an UNSAFE option. My suggestion would be to define an UNSAFE version of the existing FRAG option (see draft-ietf-tsvwg-udp-options#section-11.4 <https://datatracker.ietf.org/doc/html/draft-ietf-tsvwg-udp-options#section-11.4>) -- let's call it UFRAG -- that would allow for packet sizes greater than 65,535 bytes. The same option could be used to send singleton advanced jumbo packets as atomic fragments. This would avoid any need to modify the base UDP and UDP Options specifications. Additionally: during the review of draft-ietf-tsvwg-udp-options <https://datatracker.ietf.org/doc/html/draft-ietf-tsvwg-udp-options>, Joe Touch correctly pointed out that RFC 2765 <https://datatracker.ietf.org/doc/html/rfc2675> (and its predecessor RFC 2147 <https://datatracker.ietf.org/doc/html/rfc2147>) failed to note that it updated RFC 768 <https://datatracker.ietf.org/doc/html/rfc768>. Similar concerns apply to TCP. If this draft foes forward, it should note that it updates the UDP and TCP specifications, and it should get buy-in from TSVWG and TCPM. Thanks and regards, Mike Heard On Sun, Sep 29, 2024 at 3:51 PM C. M. Heard <he...@pobox.com> wrote: > Fred, > > I currently hold the editing pen for the changes to the UDP Options draft > that have been requested prior to the shepherd report, and my intention is > to remain silent about how, if at all, IP Parcels and Advanced Jumbos (AJs) > will support UDP Options. > > I'll provide comments on the IP Parcels and Advanced Jumbos work at a > later date, when I have spare intellectual cycles to fully comprehend the > contents of draft-templin-6man-parcels2. At this point I must confess that, > like Brian, I do not understand how a receiver will locate the options > trailer in the case of an IP Payload Length exceeding 65535. Like Joe, I > think it would be better to put the options just after the UDP header and > make a new UNSAFE option to delimit the position where the options end and > the user data begins.. But that discussion (and the corresponding update to > the UDP options draft) can occur when it is ripe; IMO that is not the case > at this time. > > Respectfully, > > Mike Heard > > On Sun, Sep 29, 2024 at 3:07 PM Templin (US), Fred L <Fred.L.Templin= > 40boeing....@dmarc.ietf.org> wrote: > >> IP parcels and Advanced Jumbos (AJs) of all sizes ranging from 1 to 2^32 >> are now eligible >> >> for using UDP options. This is just one way in which they offer a better >> service than RFC2675 >> >> Jumbograms, but there are also many others. >> >> >> >> Joe, you can either note this in your draft or just leave it be and let >> my draft do an >> >> “updates UDP options”. >> >> >> >> Thank you - Fred >> >> >> >> *From:* Brian Carpenter <brian.e.carpen...@gmail.com> >> *Sent:* Saturday, September 28, 2024 2:20 AM >> *To:* Gorry (erg) <go...@erg.abdn.ac.uk> >> *Cc:* Joe Touch <to...@strayalpha.com>; Templin (US), Fred L < >> fred.l.temp...@boeing.com>; Tim Chown <tim.ch...@jisc.ac.uk>; Internet >> Area <Int-area@ietf.org>; IPv6 List <i...@ietf.org>; tsvwg IETF list < >> ts...@ietf.org> >> *Subject:* [EXTERNAL] Re: [tsvwg] Re: UDP options [was IP Parcels and >> Advanced Jumbos (AJs)] >> >> >> >> EXT email: be mindful of links/attachments. >> >> >> >> >> That works for me.. >> >> >> >> (via tiny screen & keyboard) >> Regards, >> Brian Carpenter >> >> >> >> On Sat, 28 Sept 2024, 19:08 Gorry (erg), <go...@erg.abdn.ac.uk> wrote: >> >> See below >> >> > On 28 Sep 2024, at 04:05, Brian E Carpenter < >> brian.e.carpen...@gmail.com> wrote: >> > >> > Joe, >> > On 28-Sep-24 03:13, to...@strayalpha.com wrote: >> >>>> On Sep 27, 2024, at 7:58 AM, Templin (US), Fred L <Fred.L.Templin= >> 40boeing....@dmarc.ietf.org> wrote: >> >>> >> >>>> Indeed. But if sendmsg() and recvmsg() can and do generate RFC2675 >> packets, it means that any discussion of obsoleting RFC2675 should be >> >>>> off the table. >> >>> >> >>> No one that I know of has suggested obsoleting RFC2675 - my documents >> do not say "obsoletes" (nor even "updates”). >> >> That approach to UDP jumbo grams is incompatible with UDP options. >> >> And yes, there was a proposal to move that RFC to historic: >> >> Jones, T., G. Fairhurst, "Change Status of RFC 2675 to Historic," >> draft-jones-6man-historic-rfc2675, May 2019. >> >> We COULD have a new option with a longer length, but that’s not in our >> baseline draft. >> > >> > Wouldn't that be tricky, because the options follow the whole payload >> as I understand it? So a JumboUDPgram has to be received in full, however >> big it is, before the option saying that it's a jumbo can be received and >> interpreted. >> > >> > Where the udp-options draft says: >> > >> >>> The technique has been proposed for deprecation [Jo19]. >> > >> > I think you'd better change it to something like: >> > >> > The technique is known to be in active use in special situations, so >> cannot reasonably be deprecated. However, users of this technique cannot >> simultaneously use UDP options. >> > >> > Brian >> > >> I do not think the I-D needs to say anything about the deployment status >> of jumbograms, that another topic. >> >> I suggest if people wish, we just say that users of this technique can >> or cannot simultaneously use UDP options. >> >> Gorry >> > >> > >> >>
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