[tor-relays] growing guard probability on exits (2020-10-15)

[David Goulet]

On 16 Oct (10:49:43), nusenu wrote:
> lets see when this graph stops growing
> https://cryptpad.fr/code/#/2/code/view/1uaA141Mzk91n1EL5w0AGM7zucwFGsLWzt-EsXKzNnE/present/

To help you out here for this line:

"2020-10-15 ?? first Tor dir auths change KISTSchedRunInterval from 10 to 2"

These are the 3 authorities that notified us with the change along with the
most accurate timestamp I have timestamp:

longclaw -> Oct 14 at 16:05:08 UTC
moria1   -> Oct 14 before 16:00 UTC
  (exact consensus time is unknown, would need to dig in the votes but Roger
  said it was changed on moria "earlier today" that is before this time.)
bastet   -> Oct 15 at 15:26:47 UTC

Three are needed consensus on parameters so the Oct 15th 16:00 UTC is the
first consensus to see the change.

Keep in mind that it would take at maximum ~2h for ALL relays to get that
change.

> 
> 
> why is this relevant?
> It puts more entities into an end-to-end correlation position than there used to be
> https://nusenu.github.io/OrNetStats/#tor-relay-operators-in-end-to-end-correlation-position
> 
> and it might also decrease exit traffic on exits when a tor client chooses an exit as guard

It was pointed out by Jaym on IRC, notice here a bump in Exit capacity around
mid September:

  http://rougmnvswfsmd4dq.onion/bandwidth-flags.html?start=2020-08-18&end=2020-10-16

That could likely be a reason for this sudden change in probabilities.

Now, _maybe_ the KIST change, which in theory increases bw throughput, allowed
those Exit to push more traffic and thus might help with increasing that
Guard+Exit probability we are seeing in your graph.

Lets keep a close eye on your graph!

Thanks!
David

-- 
7h1/NAPdaaGpI8WG6X4FtryAZZ4EhnznUVVLqIf/04A=
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