Re: [quicwg/base-drafts] Refine Discussion of 0-RTT Transport Parameters (#2467)

Martin Thomson <notifications@github.com> Fri, 15 February 2019 08:58 UTC

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Subject: Re: [quicwg/base-drafts] Refine Discussion of 0-RTT Transport Parameters (#2467)
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martinthomson commented on this pull request.



> -when accepting 0-RTT data.  A server uses the transport parameters in
-determining whether to accept 0-RTT data.
-
-A server MAY accept 0-RTT and subsequently provide different values for
-transport parameters for use in the new connection.  If 0-RTT data is accepted
-by the server, the server MUST NOT reduce any limits or alter any values that
-might be violated by the client with its 0-RTT data.  In particular, a server
-that accepts 0-RTT data MUST NOT set values for the following parameters
-({{transport-parameter-definitions}}) that are smaller
-than the remembered value of those parameters.
+The value of the server's previous original_connection_id, preferred_address,
+stateless_reset_token, and ack_delay_exponent MUST NOT be used when
+establishing a new connection; rather, the client should wait to observe the
+server's new values in the handshake.
+
+The client MAY store the server's original max_ack_delay and max_packet_size

I realize now what bothered me about max_ack_delay.  This is not something you use in 0-RTT, but it is something you might remember in the same way you might remember the RTT.  It's not guaranteed to be good, but it is certainly better than the defaults for return connections.  You should remove this from this section and maybe add it where we talk about remembering the RTT (if we do that, it's late and I couldn't find it).

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