Re: [tsvwg] Alternative version of the UDP FRAG option

[Tom Herbert <[e-mail]>]

On Sat, Mar 16, 2019, 11:21 AM Joe Touch <[e-mail]> wrote:

>
>
> On Mar 16, 2019, at 9:06 AM, Tom Herbert <[e-mail]> wrote:
> Hi Mike,
>
> Thinking about this, it occurs to me be that the LITE option isn't
> needed.
>
>
> AFAICT, there is no LITE option the way you have been trying to evolve it.
>
> The assumption in the UDP options draft is that a receiver
> needs the UDP payload to immediately follow the UDP header, but the
> UDP payload can be anywhere in the surplus area as long as it's
> aligned to four bytes. A receiver will know how to handle it and
> deliver the UDP data to the application (e.g. by maintaining a pointer
> to the data).
>
> So that allows a format like:
>
> UDP header (Length=8) | Surplus area header | Options | Payload
>
>
> That’s DOA for legacy receivers.
>

Legacy receivers see a UDP datagram with zero payload, just like LITE.


> It also basically kills zero-copy.
>

Exactly how does it do that?


> Which looks a whole lot like any other protocol format with a variable
> length header such as TCP or IPv4.
>
>
> There needs to be a justification for giving up the two features above,
> something beyond “looks”.
>
> I don’t recall seeing one yet - if there is, can you remind me so I can
> include it in the summary of these excursions?
>
> Joe
>
>