[bittorrent] BT proxy

Andrew Brampton andrew at bramp.freeserve.co.uk
Tue Apr 12 11:26:17 EDT 2005

I believe there was a commercial product that claims BitTorrent proxying

It was a transparent proxy that would watch all BitTorrent connection. It
would identify them as BitTorrent by either port inspection (ie 6881-) or by
packet inspection (I believe its trivial to watch the first 20 bytes for
"BitTorrent Protocol").

Once it is watching a connection it will associate that TCP Flow with the
Torrent's hash (which it saw in a first packets). Then every time it sees a
piece message it would keep a copy of the data inside. Now next time another
client is transparently connected to the same BitTorrent swarm the proxy can
intercept all outgoing request packets and return the piece itself (as long
as it already has it cached).

This concept is very similar to a web proxy except in this case the BT Proxy
is doing anything transparently, and never actually making any requests to
the outside world.

I believe the commercial product that does this was aimed at ISPs that
wanted to cache P2P traffic inside their own network to save themselves
external bills.

The idea is sound, and would be a nice Open Source project that university
campus or business networks etc could use.


----- Original Message ----- 
From: "David P. Mott" <dpmott at sep.com>
To: <bittorrent at lists.ibiblio.org>
Sent: Tuesday, April 12, 2005 3:58 PM
Subject: [bittorrent] BT proxy

> Some people have brought up the need for a BT proxy, but all attempts at 
> discussion on that topic were more or less ignored on the yahoo forum. The 
> quote that comes to mind is that "a BT proxy is an unfirewalled BT 
> client" -- which shows that the author either didn't grasp the real need 
> for a true proxy, or didn't care.
> Thanks,
> -dpmott

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