Re: [quicwg/base-drafts] Prioritize Handshake probe packet over Short packet (#3583)

Tatsuhiro Tsujikawa <notifications@github.com> Wed, 15 April 2020 13:23 UTC

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Date: Wed, 15 Apr 2020 06:23:27 -0700
From: Tatsuhiro Tsujikawa <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] Prioritize Handshake probe packet over Short packet (#3583)
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As discussed in neqo issue thread, which packet number spaces should be chosen depends on the situation.
ngtcp2 sends Initial and Handshake probes at the same time if server sees they are in-flight when PTO timer fires so that it can coalesce them and also handle the situation that client might drop Initial key.  This is a deviation from the draft-27.
For the particular situation that this issue describes, I think client can just send Handshake probe packet.  If server still has Handshake key, it will respond with Handshake packet.  If not, then it will send HANDSHAKE_DONE frame in Short packet, and client confirms handshake completion.
Sending Short probe with Handshake packet might reduce the time before client reacts the lost Short packet, but might be discarded if server does not have appropriate key.

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