In the Tor manpage I read about CircuitBuildTimeout. It is set to a default value of 60 seconds. However usually also LearnCircuitBuildTimeout is set. This enables adaptive learning of those timeouts. Does this setting only affect the current Tor session or is it saved over various sessions?


According to the specification (see section 2.4.2.) CircuitBuildTimeout is used across sessions.

Timeouts are stored on disk in a histogram of 50ms bin width, the same width used to calculate the Xm value above. This histogram must be shuffled after being read from disk, to preserve a proper expiration of old values after restart.

The specification includes the following, too:

The Tor client should build test circuits at a rate of one per minute up until 100 circuits are built. This allows a fresh Tor to have a CircuitBuildTimeout estimated within 1.5 hours after install, upgrade, or network change (see below).

which wouldn't be included if an already used Tor would need the same amount of time.

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