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

Joe Touch <touch@strayalpha.com> Sat, 16 March 2019 18:21 UTC

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From: Joe Touch <touch@strayalpha.com>
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Date: Sat, 16 Mar 2019 11:21:32 -0700
Cc: "C. M. Heard" <heard@pobox.com>, tsvwg <tsvwg@ietf.org>
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To: Tom Herbert <tom@herbertland.com>
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Subject: Re: [tsvwg] Alternative version of the UDP FRAG option
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> On Mar 16, 2019, at 9:06 AM, Tom Herbert <tom@herbertland.com> 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.

It also basically kills zero-copy.

> 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

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