Re: Transmission of IPv6 Jumbograms as Atomic Fragments

[Bob Hinden <[e-mail]>]

Justin,

On Nov 18, 2021, at 6:00 AM, Justin Iurman <[e-mail]> wrote:
> 
> Bob,
> 
> If this one can help, I remember a talk [1] ("Big TCP", slides and video both available) back to July during the Netdev conference. The main idea is to use IPv6 Jumbograms to reduce the overhead of the TCP stack. It is used internally by Google.
> 

Thanks, that is interesting.  However, unlike what Fred is proposing, they are using it to send larger packets (that is, what Jumbograms were designed to do), not add a fragmentation header to get an identification field (an not send packets larger than can be done in the IPv6 base header).

Bob



> Justin
> 
>  [1] https://netdevconf.info/0x15/session.html?BIG-TCP
> 
>> Fred,
>> 
>>> On Nov 17, 2021, at 3:39 PM, Templin (US), Fred L <[e-mail]>
>>> wrote:
>>> 
>>> Let me add a bit more clarity, then. IPv6 made a bit of a mistake when it
>>> presumed that the
>>> only reason a packet might need an Identification value was to support the
>>> fragmentation
>>> and reassembly process.
>> 
>> If what you want is some sort of identification field, it would be easier for
>> you to propose an extension header that does that and see if you can build a
>> consensus around that.
>> 
>> In my view, trying to do that by modifying IPv6 Jumbograms (that I don’t know of
>> anyone uses these days) to include a fragment header, makes little sense to me.
>> 
>> Bob
>> 
>> 
>> 
>>> Hence, the Identification was strictly tied to the Fragment Header.
>>> But, it turns out there are other reasons to include an unpredictable ID with an
>>> IPv6 packet
>>> (jumbos included) that have nothing to do with fragmentation. Since the only way
>>> to get
>>> an Identification in IPv6-land is to include a Fragment Header, then that is
>>> just what we are
>>> going to have to do. – again, jumbos included.
>>> 
>>> Thanks - Fred
>>> 
>>> From: David Farmer [mailto:[e-mail]]
>>> Sent: Wednesday, November 17, 2021 3:27 PM
>>> To: Templin (US), Fred L <[e-mail]>
>>> Cc: 6man <[e-mail]>; Brian E Carpenter <[e-mail]>
>>> Subject: Re: [EXTERNAL] Re: Transmission of IPv6 Jumbograms as Atomic Fragments
>>> 
>>> While I see no reason to depreciate RFC2675, without evidence of actual active
>>> use of jumbograms or at least an intent to use them, but for the issue you
>>> describe prevents it, I see no reason to advance the update you propose.
>>> 
>>> Even in the R&E networking community where we make regular use of data grams
>>> larger than 1500 bytes, I’m not aware of the use of, or even a desire to use,
>>> jumbograms.
>>> 
>>> Thanks
>>> 
>>> On Wed, Nov 17, 2021 at 16:45 Templin (US), Fred L <[e-mail]>
>>> wrote:
>>> Brian, I came through the supercomputer lab at NASA Ames in Mt View CA in 1996/7
>>> where HiPPI was heavily used. I didn't spend much time there, but enough to get
>>> a
>>> rough read that large packets are plausible.
>>> 
>>> At some time not long after that, I had the good fortune to meet Dave Borman and
>>> asked him about RFC2675 with a "YMBK" pre-disposition toward the concept. Dave
>>> assured me that the document was serious, and I do not see evidence that it has
>>> been deprecated.
>>> 
>>> So, do I know of any such mega-links? Not offhand, but AFAICT RFC2675 is still
>>> part
>>> of the IPv6 architecture and needs to be honored as such.
>>> 
>>> Thanks - Fred
>>> 
>>>> -----Original Message-----
>>>> From: Brian E Carpenter [mailto:[e-mail]]
>>>> Sent: Wednesday, November 17, 2021 1:39 PM
>>>> To: Templin (US), Fred L <[e-mail]>; 6man <[e-mail]>
>>>> Subject: [EXTERNAL] Re: Transmission of IPv6 Jumbograms as Atomic Fragments
>>>> 
>>>> EXT email: be mindful of links/attachments.
>>>> 
>>>> 
>>>> 
>>>> Fred,
>>>> 
>>>> Is there any evidence of usage of jumbograms? To my knowledge, even the high
>>>> energy phsyics community, one of the main proponents of
>>>> jumbograms back in the days when HIPPI seemed important, doesn't use them,
>>>> despite extensive use of IPv6 for bulk data.
>>>> 
>>>> Regards
>>>>    Brian
>>>> 
>>>> On 18-Nov-21 06:54, Templin (US), Fred L wrote:
>>>>> Here is a new draft that may be of interest. It is a quick read (~2pgs) and
>>>>> proposes to
>>>>> update RFC2675 by permitting transmission of IPv6 jumbograms as atomic
>>>>> fragments.
>>>>> 
>>>>> Please post comments to the list.
>>>>> 
>>>>> Fred
>>>>> 
>>>>> -----Original Message-----
>>>>> From: I-D-Announce [mailto:[e-mail]] On Behalf Of
>>>>> [e-mail]
>>>>> Sent: Wednesday, November 17, 2021 9:09 AM
>>>>> To: [e-mail]
>>>>> Subject: I-D Action: draft-templin-6man-jumbofrag-00.txt
>>>>> 
>>>>> 
>>>>> A New Internet-Draft is available from the on-line Internet-Drafts directories.
>>>>> 
>>>>> 
>>>>>         Title           : Transmission of IPv6 Jumbograms as Atomic Fragments
>>>>>         Author          : Fred L. Templin
>>>>>    Filename        : draft-templin-6man-jumbofrag-00.txt
>>>>>    Pages           : 4
>>>>>    Date            : 2021-11-17
>>>>> 
>>>>> Abstract:
>>>>>    Internet Protocol, Version 6 (IPv6) provides a service for
>>>>>    transmission of IPv6 packets larger than 65,535 octets known as
>>>>>    "jumbograms".  Such large packets are not eligible for fragmentation,
>>>>>    and the current specification forbids the inclusion of a fragment
>>>>>    header of any kind.  However, some implementations may wish to
>>>>>    include an Identification value with each jumbogram; hence this
>>>>>    document proposes the transmission of IPv6 jumbograms as "atomic
>>>>>    fragments".
>>>>> 
>>>>> 
>>>>> The IETF datatracker status page for this draft is:
>>>>> https://datatracker.ietf.org/doc/draft-templin-6man-jumbofrag/
>>>>> 
>>>>> There is also an htmlized version available at:
>>>>> https://datatracker.ietf.org/doc/html/draft-templin-6man-jumbofrag-00
>>>>> 
>>>>> 
>>>>> Internet-Drafts are also available by anonymous FTP at:
>>>>> ftp://ftp.ietf.org/internet-drafts/
>>>>> 
>>>>> 
>>>>> _______________________________________________
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>>>>> or ftp://ftp.ietf.org/ietf/1shadow-sites.txt
>>>>> 
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