Re: [tsvwg] Comment on "draft-ietf-tsvwg-udp-options-28" -> do we need to update the text oin the Length Field

[Joe Touch <[e-mail]>]

No need to- it’s actually correct.  A udp payload length of zero is a udp length of 8.

I’ll put that in as a clarification via this thread.

> On Dec 22, 2023, at 9:05 AM, C. M. Heard <[e-mail]> wrote:
> 
> 
>> On Fri, Dec 22, 2023 at 8:51 AM Gorry Fairhurst wrote:
> 
>>> On 22/12/2023 15:18, C. M. Heard wrote:
>>> On Fri, Dec 22, 2023 at 1:45 AM Gorry Fairhurst wrote:
>>>> ... <snip discussion on options for jumbograms> ...
>>>> 
>>>> I have two questions, intended to help focus on any needed changes:
>>>> 
>>>> 
>>>> 1) I found one instance of text in the current draft that might benefit
>>>> from a change, to avoid a potential mis-read:
>>>> 
>>>> The current draft contains: "The UDP option area can be used with any
>>>> UDP payload length (including zero)",
>>>> 
>>>> - If I understand, I think it would be helpful to clarify that this is
>>>> the case of "zero-length user data", rather than the length field of the
>>>> UDP header, e.g.:
>>>> 
>>>> "The UDP option area can be used with any length of UDP user data
>>>> (including zero).
>>>> A datagram with zero-length user data results in a UDP Length field
>>>> value of 8."
>>>> 
>>> 
>>> That sounds right to me.
>>>  
>>>> 
>>>> 2) Does this draft also need to deal with UDP Length = 0?
>>> 
>>> No.
>>> 
>>>> 
>>>> I understand, the length field is zero, as a special case for the IPv6
>>>> Jumbogram, but I suggest this could be a seperable topic. One suitable
>>>> approach could be to keep the updates to define this with the PS spec
>>>> that defines the change in the UDP processing, and for example to only
>>>> note that:
>>>> 
>>>> "If UDP options is defined for UDP datagrams with a length field less
>>>> than 8, a specification would need to to define whether and how this
>>>> format identifies the presence of UDP options."
>>> 
>>> I don't think we should do even that. The proposed text in
>>> https://github.com/tsvwg/draft-ietf-tsvwg-udp-options/issues/26
>>> adequately addresses the issue raised by IPv6 Jumbograms,
>>> which is that in that case the UDP packet has no independent
>>> UDP Length, and the fact that this arises from UDP Length == 0
>>> is incidental.
>>> 
>>> Given there are no other known or proposed uses of values
>>> of UDP Length <  8, I think we can leave it at that.
>>> 
>>> Mike Heard
>>> 
>> I'd personally be happy with both of your suggerstions!
>> 
> Perhaps, then, open a github issue for #1 above?
> 
> Mike