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Stop using initial timeout #4263

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merged 3 commits into from Nov 3, 2020
Merged

Stop using initial timeout #4263

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2719b29
Stop using initial timeout
martinthomson Oct 27, 2020
ec93558
Remove formula with confusing variables
martinthomson Oct 28, 2020
a9d9aeb
initial RTO comparison
martinthomson Oct 30, 2020
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6 changes: 1 addition & 5 deletions draft-ietf-quic-transport.md
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Expand Up @@ -2255,11 +2255,7 @@ Endpoints SHOULD abandon path validation based on a timer. When setting this
timer, implementations are cautioned that the new path could have a longer
round-trip time than the original. A value of three times the larger of the
current Probe Timeout (PTO) or the PTO for the new path (that is, using
kInitialRtt as defined in {{QUIC-RECOVERY}}) is RECOMMENDED. That is:

~~~
validation_timeout = 3*max(PTO_current, PTO_new)
~~~
kInitialRtt as defined in {{QUIC-RECOVERY}}) is RECOMMENDED.
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Can we add the computation back in? With the corrected values of course:

That is, validation timeout = max(3*PTO, 9*kInitialRtt)

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But that is wrong. Because the PTO on the new path is 9*kInitialRtt on the handshake, but 9*kInitialRtt + 3*max_ack_delay on migration.

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Oh hm. It's actually more than that, since rttvar is also set to kInitialRtt/2 initially. Ok, let's leave it as you have it then.


This timeout allows for multiple PTOs to expire prior to failing path
validation, so that loss of a single PATH_CHALLENGE or PATH_RESPONSE frame
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