[tsvwg] Re: [EXTERNAL] Re: Re: UDP options [was IP Parcels and Advanced Jumbos (AJs)]

["Templin (US), Fred L" <[e-mail]>]

Tom,

> Let me rephrase. Does the GRO/GSO implementation need to change because of IP parcels?

You are more qualified to answer this question than I am.

From: Tom Herbert <tom=[e-mail]>
Sent: Friday, November 15, 2024 10:43 AM
To: Templin (US), Fred L <[e-mail]>
Cc: C. M. Heard <[e-mail]>; Gorry Fairhurst <[e-mail]>; Joe Touch <[e-mail]>; int-area <[e-mail]>; 6man <[e-mail]>; TSVWG <[e-mail]>
Subject: Re: [tsvwg] Re: UDP options [was IP Parcels and Advanced Jumbos (AJs)]

On Fri, Nov 15, 2024, 6:30 PM Templin (US), Fred L <Fred.L.Templin=[e-mail]<mailto:[e-mail]>> wrote:
Tom,

>Is there any interaction between GRO/GSO and IP parcels then?

An IP parcel is exactly a multi-segment GSO buffer packaged for transmission over an Internetwork.

Hi Fred,

Let me rephrase. Does the GRO/GSO implementation need to change because of IP parcels?

Tom

Fred

From: Tom Herbert <tom=[e-mail]<mailto:[e-mail]>>
Sent: Friday, November 15, 2024 10:09 AM
To: Templin (US), Fred L <[e-mail]<mailto:[e-mail]>>
Cc: C. M. Heard <[e-mail]<mailto:[e-mail]>>; Gorry Fairhurst <[e-mail]<mailto:[e-mail]>>; Joe Touch <[e-mail]<mailto:[e-mail]>>; int-area <[e-mail]<mailto:[e-mail]>>; 6man <[e-mail]<mailto:[e-mail]>>; TSVWG <[e-mail]<mailto:[e-mail]>>
Subject: Re: [IPv6]Re: [EXTERNAL] Re: [tsvwg] Re: UDP options [was IP Parcels and Advanced Jumbos (AJs)]

On Fri, Nov 15, 2024, 6:01 PM Templin (US), Fred L <Fred.L.Templin=[e-mail]<mailto:[e-mail]>> wrote:
Hi Mike,

This is exactly what happens with Generic Segment Offload (GSO) and Generic Receive Offload (GRO) in real networks today. After a multi-segment GSO buffer is broken into individual IP packets during packetization, the receiver applies GRO to restore the multi-segment buffer if possible; otherwise, it delivers the individual IP packets to the upper layer. Each individual IP packet is an atomic unit that will be understood by upper layers even if it is not restored into the original multi-segment buffer originally prepared by GSO. This is the way GSO/GRO work today, and IP parcels does not change that.

Hi Fred,

Is there any interaction between GRO/GSO and IP parcels then?

Tom


Fred

From: C. M. Heard <[e-mail]<mailto:[e-mail]>>
Sent: Friday, November 15, 2024 9:36 AM
To: Templin (US), Fred L <[e-mail]<mailto:[e-mail]>>
Cc: Gorry Fairhurst <[e-mail]<mailto:[e-mail]>>; Joe Touch <[e-mail]<mailto:[e-mail]>>; int-area <[e-mail]<mailto:[e-mail]>>; 6man <[e-mail]<mailto:[e-mail]>>; TSVWG <[e-mail]<mailto:[e-mail]>>
Subject: [EXTERNAL] Re: [tsvwg] Re: UDP options [was IP Parcels and Advanced Jumbos (AJs)]

EXT email: be mindful of links/attachments.


Fred,

I very strongly disagree  with your statement that it is not an error to "it will instead deliver each of the individual IP packets to upper layers without restoring the parce."

That amounts to delivering PIECES of the UDP packet sent by the originator to the upper layer. This would be exactly equivalent to allowing a receiver that does not understand the UDP FRAG option to deliver the payload of each individual fragment to the upper layer. The UDP options draft  goes to considerable effort to ensure that this does not happen.

There is long-standing precedent that the boundaries of UDP datagrams are preserved during transmission across the Internet. Many if not all UDP-based protocols depend on that, explicitly or implicitly. I do not understand why this point is even considered open for discussion.

Mike

On Fri, Nov 15, 2024 at 8:26 AM Templin (US), Fred L <[e-mail]<mailto:[e-mail]>> wrote:
Hi Mike,

Thank you for looking and commenting. A UDP/IP parcel containing N segments that undergoes packetization somewhere along the path will arrive at the final destination as N individual IP packets, each containing a Parcel Parameters UDP option. If the destination recognizes the option, it will restore the N segment parcel within the kernel before delivering the entire parcel as a single unit to upper layers. If the destination does not recognize the option, it will instead deliver each of the individual IP packets to upper layers without restoring the parcel which is not an error. Very significantly, each of the individual IP packets can be dealt with as standalone units once packetization has been applied; it is just that if the receive-side does not apply restoration (i.e., GRO) the performance optimization will be lost at that end. So, I don’t think there is any problem to worry about.

Fred Templin

From: C. M. Heard <[e-mail]<mailto:[e-mail]>>
Sent: Thursday, November 14, 2024 4:55 PM
To: Templin (US), Fred L <[e-mail]<mailto:[e-mail]>>
Cc: Gorry Fairhurst <[e-mail]<mailto:[e-mail]>>; Joe Touch <[e-mail]<mailto:[e-mail]>>; int-area <[e-mail]<mailto:[e-mail]>>; 6man <[e-mail]<mailto:[e-mail]>>; TSVWG <[e-mail]<mailto:[e-mail]>>
Subject: Re: [tsvwg] Re: UDP options [was IP Parcels and Advanced Jumbos (AJs)]

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 2675<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 <[e-mail]<mailto:[e-mail]>> 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=[e-mail]<mailto:[e-mail]>> 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 <[e-mail]<mailto:[e-mail]>>
Sent: Saturday, September 28, 2024 2:20 AM
To: Gorry (erg) <[e-mail]<mailto:[e-mail]>>
Cc: Joe Touch <[e-mail]<mailto:[e-mail]>>; Templin (US), Fred L <[e-mail]<mailto:[e-mail]>>; Tim Chown <[e-mail]<mailto:[e-mail]>>; Internet Area <[e-mail]<mailto:[e-mail]>>; IPv6 List <[e-mail]<mailto:[e-mail]>>; tsvwg IETF list <[e-mail]<mailto:[e-mail]>>
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), <[e-mail]<mailto:[e-mail]>> wrote:
See below

> On 28 Sep 2024, at 04:05, Brian E Carpenter <[e-mail]<mailto:[e-mail]>> wrote:
>
> Joe,
> On 28-Sep-24 03:13, [e-mail]<mailto:[e-mail]> wrote:
>>>> On Sep 27, 2024, at 7:58 AM, Templin (US), Fred L <Fred.L.Templin=[e-mail]<mailto:[e-mail]>> 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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