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Re: [tsvwg] UDP options and header-data split (zero copy)

Joseph Touch <touch@strayalpha.com> Mon, 19 July 2021 21:32 UTC

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From: Joseph Touch <touch@strayalpha.com>
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Date: Mon, 19 Jul 2021 14:32:38 -0700
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To: Tom Herbert <tom@herbertland.com>
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Subject: Re: [tsvwg] UDP options and header-data split (zero copy)
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Hi, Tom,

First, there’s a good reason to not assume we can put the fragment “whole packet” options in the first fragment: size. We currently have no limit on how much space options can use in general. Per-fragment options clearly need to fit inside the fragment with fragment data. But the options on the reassembled packet might be difficult to assume can be contained in the first fragment alone.

Further, you have proposed several scenarios that claim that users may either want or need to not support legacy mode UDP options, but do want to use fragment-based options. That’s not permitted in the current spec and never has been.

Mode is chosen by the transmitter, not the receiver. Support for legacy mode has always been required.

Further, putting a functionality limit (either in length or support for legacy mode) to enhance the performance of some implementations doesn’t seem prudent.

Joe

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