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Re: [quicwg/base-drafts] PMTUD (#64)

martinduke <notifications@github.com> Mon, 05 December 2016 23:14 UTC

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Date: Mon, 05 Dec 2016 15:14:24 -0800
From: martinduke <notifications@github.com>
To: quicwg/base-drafts <base-drafts@noreply.github.com>
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Subject: Re: [quicwg/base-drafts] PMTUD (#64)
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"(b) is semi-practical, but the checksum is still computable by a passive observer."

Indeed, all ICMP is vulnerable to a passive observer, but if the header echo isn't there it's vulnerable to *off-path* attacks that guess the 4-tuple.

It seems odd to spend an enormous amount of energy to save a handful of bytes in headers and frames, and then turn around and use a conservatively low MTU, when a very common IPv4 UDP MSS is 1472 Bytes.

Regarding option (c), it makes a lot of sense for CHLO to be a max-size packet for these purposes, but it's not sufficient. Furthermore, using loss as the signal instead of ICMP seems like an inefficient solution.

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