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Re: different IP address for each request?


----- Original Message ----
From: Roger Dingledine <arma@xxxxxxx>
To: or-talk@xxxxxxxxxxxxx
Sent: Saturday, August 5, 2006 10:45:19 AM
Subject: Re: different IP address for each request?

On Tue, Jul 25, 2006 at 03:54:01PM -0700, Eric H. Jung wrote:
> How can I configure torrc such that every request goes through
>a different exit node (i.e., I get a different IP address for each
>request)? This isn't a browser so I'm not able to control keep-alive
>unless I do at the OS level (is there a way to do that on Windows?)

The short answer is that we don't want you to do that. The reason is that
you'd be building a new circuit for every request, and building a circuit
puts a non-trivial load on the Tor servers. If everybody tried to build
new circuits often, most circuits would fail to be built (because the
Tor servers can't keep up), all the Tor servers would run at 100% cpu,
which would ultimately cause the operators to stop running the servers.

We know this, because a few years back we experienced it. At that point
the default amount of time for rotating circuits was 30 seconds, rather
than 10 minutes.

While I'm at it, there's another point to make. Tor only rebuilds a
circuit if the previous one has been used. So we don't put any load
on the network except when we're actually browsing the web or whatever
we're doing. This lets the available Tor servers (700 or so) time-share
over the number of users (several hundred thousand, but not all active
at the same time). So the critical lesson is that we need to make sure
that the tools we write that help us use Tor don't make frequent requests
to Tor while we're not actively using it.

Hope that helps,