exit nodes always also being middle nodes

[Roger Dingledine]

On Sun, Nov 02, 2008 at 08:50:11AM -0500, Erilenz wrote:
> If you run as an exit node, it's my understanding that you also act as a
> middleman node. Would it be possible, and would it be a good idea, to
> add an option such that you only act as an exit node?
> 
> It seems a bit of a waste to use potential exit bandwidth as middleman
> relaying bandwidth when exit bandwdith is more scarce.

Actually, clients weight their path selection based on whether you're
an exit. So they look at how scarce exit bandwidth is, and choose your
exit proportionally less for non-exit positions.

See
https://www.torproject.org/documentation.html.en#DesignDoc
which points to
https://svn.torproject.org/svn/tor/trunk/doc/spec/path-spec.txt
and section 2.2 explains more.

We also do a similar weighting for the entry position (see section 5).

--Roger