Re: [quicwg/base-drafts] Clarify when the PTO may need to be recomputed and reset (#3665)

Jana Iyengar <> Tue, 19 May 2020 22:02 UTC

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Date: Tue, 19 May 2020 15:02:12 -0700
From: Jana Iyengar <>
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Subject: Re: [quicwg/base-drafts] Clarify when the PTO may need to be recomputed and reset (#3665)
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@janaiyengar commented on this pull request.

> +PTO period being set to twice its current value. The PTO backoff is reset upon
+receiving an acknowledgement, except when a client receives an acknowledgment
+from a server prior to the server validating the client address. A client
+keeps increasing the PTO backoff until the server's address validation
+completes to ensure the client's PTO timer is not set too aggressively
+when the server is slow in responding with handshake data.

PTO period being set to twice its current value. The PTO backoff factor is reset
when an acknowledgement is received, except in the following case. A server
might take longer to respond to packets during the handshake than otherwise.
To protect such a server from repeated client probes, the PTO backoff is not
reset at a client that is not yet certain that the server has finished validating
the client's address. That is, a client does not reset the PTO backoff factor on
receiving acknowledgements until it receives a HANDSHAKE_DONE frame or
an acknowledgement for one of its Handshake or 1-RTT packets.

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