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

Martin Thomson <notifications@github.com> Tue, 19 May 2020 00:53 UTC

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Date: Mon, 18 May 2020 17:53:34 -0700
From: Martin Thomson <notifications@github.com>
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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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@martinthomson commented on this pull request.



>  
 When a PTO timer expires, the PTO backoff MUST be increased, resulting in the
-PTO period being set to twice its current value.  The PTO period is set based
-on the latest RTT information after receiving an acknowledgement. The PTO
-backoff is reset upon receiving an acknowledgement unless it's a client unsure
-if the the server has validated the client's address. Not resetting the backoff
-during peer address validation ensures the client's anti-deadlock 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 is reset upon
+receiving an acknowledgement unless it's a client unsure if the server has

The subject of the "it" is a little unclear here.

Perhaps instead:

> The PTO backoff is reset when receiving an acknowledgment, except when a client receives an acknowledgment from a server prior to the server validating the client address.  A client MUST keep increasing the PTO count until <insert clear conditions here>.

>  
 When a PTO timer expires, the PTO backoff MUST be increased, resulting in the
-PTO period being set to twice its current value.  The PTO period is set based
-on the latest RTT information after receiving an acknowledgement. The PTO
-backoff is reset upon receiving an acknowledgement unless it's a client unsure
-if the the server has validated the client's address. Not resetting the backoff
-during peer address validation ensures the client's anti-deadlock 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 is reset upon
+receiving an acknowledgement unless it's a client unsure if the server has
+validated the client's address. Not resetting the backoff during peer address
+validation ensures the client's anti-deadlock timer is not set too aggressively

This is the first use of anti-deadlock in the draft.  I think that you are just referring to the PTO timer that we set unconditionally on the client prior to address validation.

It might be better to keep all the rules about setting the "PTO timer" at the client prior to address validation in the one paragraph/section rather than scattering them about like this.  Then you can say "except at the client prior to address validation; see {{...}}".

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