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Re: purging old router information, revocation

Nick Mathewson wrote:
On Wed, Feb 21, 2007 at 02:09:31PM -0500, James Muir wrote:
I'd like to know how directories are cleaned up after a router leaves the Tor network. I've read through the specs distributed with but I haven't been able to find a discussion on this.

Hm. You're right; this isn't documented well enough. Let me dig through the code a little.

Once your router is no longer publishing router descriptors, the clock
starts ticking: it will no longer be included in the network status
documents the authorities generate after it's older then
MAX_AGE_TO_PUBLISH seconds old (currently, 20 hours, though we're
going to crank this up to something higher so clients don't need to
publish so often), the authorities won't include it in the network
status documents they generate.

Some clients may ask caches for the descriptor anyway, since they may
have older network status documents.  Caches throw even old expired
descriptors away after  OLD_ROUTER_DESC_MAX_AGE (currently 5 days).

It would be cool to have a patch to dir-spec.txt to document this
stuff, if it's not documented there somewhere already. :)

Thank-you for explaining this. I agree that it would be very nice to have this documented in dir-spec.txt. It is definitely not discussed there now.

One thing that I couldn't find any reference to in the comments in the source code is how long directory authorities will keep trying to connect to an onion router that is not responding. Is this also 20 hours? There is a discussion about what Tor clients do when one of their entry guards stops responding but I would guess that directory authorities probably behave differently.