Re: [quicwg/base-drafts] use a HANDSHAKE_DONE frame to drive the handshake to confirmation (#3145)

[Kazuho Oku <[e-mail]>]

kazuho commented on this pull request.



> @@ -760,14 +756,9 @@ and ignoring any outstanding Initial packets.
 
 ### Discarding Handshake Keys
 
-An endpoint MUST NOT discard its handshake keys until the TLS handshake is
-confirmed ({{handshake-confirmed}}).  An endpoint SHOULD discard its handshake
-keys as soon as it has confirmed the handshake.  Most application protocols
-will send data after the handshake, resulting in acknowledgements that allow
-both endpoints to discard their handshake keys promptly.  Endpoints that do
-not have reason to send immediately after completing the handshake MAY send
-ack-eliciting frames, such as PING, which will cause the handshake to be
-confirmed when they are acknowledged.
+An endpoint MUST discard its handshake keys when the TLS handshake is confirmed
+({{handshake-confirmed}}).  The server MUST send a HANDSHAKE_DONE frame within
+one round-trip time of handshake completion.

I think "within one round-trip time" is too long. As this happens before both endpoints have good estimation of RTT, it could well be the case that the server's estimated RTT be much greater than the PTO of the client. In such case, it would seem to the client as if the CF had been lost.

I think we should say "SHOULD immediately send", with possibly acknowledging the fact that the server "can bundle the HANDSHAKE_DONE frame with 0.5 RTT data."

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