[tor-talk] IDEA: Compress traffic at exit

[Andrew Lewman]

On Fri, 20 Jan 2012 20:34:27 +0100
"Sebastian G. <bastik.tor>" <bastik.tor at googlemail.com> wrote:
> Overview:
> 
>    This is about compressing traffic at the exit, where it's passed
> from outside the network through other relays to the client where it
>    gets decompressed.

And what decompresses the traffic at the destination site?

>    The network has a high bandwidth usage due to it massive user-base.
>    This idea should reduce the outgoing traffic of the exit and take
>    much load from the mid-relay and the entry point.

Lack of bandwidth isn't so much the problem. Lack of tcp sockets and cpu
power for onionskins at the relays is the problem. The higher bandwidth
the relay, the worse these two problems become. 

>    The relays (exit or not) have certain bandwidth limitations which
> may could be circumvented by compressing the traffic they have to
> handle, which would mean that they could handle more users.

Exit relays are already overloaded, adding compression overhead will
not make this better. 

Lots of traffic on the Internet is already compressed between the
client and server. What tor does in the middle is irrelevant. See the
SPDY proposal,
https://gitweb.torproject.org/torspec.git/blob/HEAD:/proposals/ideas/xxx-using-spdy.txt

Generally, the tor relays do not want to touch nor modify user traffic
in any way. Once we can detect "compress or not", it's a quick slide
down a slippery slope to "censor or not". See
https://trac.torproject.org/projects/tor/wiki/doc/TorFAQ#YoushouldchangeTortopreventusersfrompostingcertaincontent.

-- 
Andrew
http://tpo.is/contact
pgp 0x74ED336B