Re: [quicwg/base-drafts] Coalescing Packet including Initial Packet would be over the MTU (#1546)

Kazuho Oku <notifications@github.com> Fri, 13 July 2018 00:21 UTC

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Subject: Re: [quicwg/base-drafts] Coalescing Packet including Initial Packet would be over the MTU (#1546)
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> It is way simpler to send the client initial as is, and the 0-RTT data in a follow-up packet. If the implementation can predict that a 0-RTT will follow, it can refrain from padding the Initial packet, and make sure that the coalesced 0-RTT packet extends to the specified limit. Doable, even if not entirely natural.

FWIW, you have the freedom to pad the 0-RTT packet of a coalesced datagram instead. IMO that is the natural way to combine Initial and 0-RTT into a single datagram.

What picotls does when both 0-RTT key is available is:
* construct Initial packet without padding
* construct 0-RTT packet coalesced to the Initial
* pad the 0-RTT packet if the datagram is going to be to small

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