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Re: opening up (exit policy) a bit ...

Thus spake John Case (case@xxxxxxxxxxxxxxxx):

> So I am indeed an exit...
> >>This is totally incorrect. Tor uses exit nodes in the middle and possibly
> >>even guard position, depending on flags and general scarcity of
> >>guards.
> Ok, that was the answer to my first question.  My follow-up questions 
> were:
> If that is the case, is the distribution random ?  Or is there some 
> expected ratio I should see between non-exit relay traffic and port 80 
> exit traffic ?

As of Tor, the ratios used by clients is listed in the
consensus[1]*. See sections 3.2 and 3.4.3 of dir-spec.txt

> Have I complicated that ratio by having a very restrictive exit policy, or 
> doesn't that matter ?
> (FWIW, I picked port 80 just as an example)

You have, sort of. Because you do not exit to enough ports to get the
'Exit' flag, you will be treated as a middle or Guard-only node,
depending upon your uptime. This means the following weights will
apply to you in each of the three positions:

Guard: Wgg (if you are a Guard, otherwise 0)
Middle: Wmg (if you are a Guard, otherwise Wmm)
Exit: Weg (if you are a Guard, otherwise Wem)

In the current weight implementation we

"Handle bridges and strange exit policies:
     Wgm=Wgg, Wem=Wee, Weg=Wed"

This means that your non-Exit flagged node will be weighted like an
Exit flagged node for the exit position, but will be weighted as if
you were a non-scarce middle or guard node for the other positions.

In sort, you would in theory get slightly more total load than if you
were an actual Exit.

As to the ratio of your exit to non-exit load, that depends heavily on
if you have the Guard flag, if you are a Directory Mirror, what
percentage of the exit traffic actually flows over port 80, and how
many clients have upgraded to the new algorithm vs the old.

*[1]. If there is a bug or other issue, these weights may be
temporarily absent from the consensus. Currently, Bug 1294 is causing
us to drop weights when there are no Guard+Exit flagged nodes, which
can happen when Exits are scarce. When weights are absent, clients
fall back to the previous client-based weighting algorithm. By not
having an actual 'Exit' flag, you will be treated as a non-scarce
Guard or middle node for purposes of this old algorithm too, and
should see more load accordingly.

Mike Perry
Mad Computer Scientist
fscked.org evil labs

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