Reduce hops when privacy level allows to save Tor network bandwidth

[Georg Sluyterman]

Erilenz wrote, On 2009-11-17 14:57:
> The following occured to me. Tor is designed to protect users from
> traffic analysis by very technical adversaries. There are many use
> cases where that level of protection isn't required. In those cases,
> if there was a config option to reduce the number of hops in a circuit
> to 2 (or possibly even 1), then users would be able to get themselves a
> more responsive circuit, whilst saving the Tor network overall
> bandwidth.
> 
> In a three hop circuit, when x contacts y, the Tor network ends up
> having to transfer 4X the data:
> 
> x -(1)> Entry -(2)> Middle -(3)> Exit -(4)> y
> 
> In a 2 hop circuit it only has to transfer 75% of that:
> 
> x -(1)> Entry -(2)> Exit -(3)> y
> 

If you send a 1 kByte packet through a Tor node (lets forget the
overhead for now), the Tor node has to download the packet and upload it
to the next node (or endpoint) which equals 2 kByte traffic on the
internetconnection for the specific Tor node.

If you send a 1 kByte packet through Tor (again forget about overhead)
the traffic used in the network will be ~6 kByte (packetsize * 2 *
number_of_hops).

If you send through two hops instead of three, you will genereate 4
kByte traffic instead of 6 kByte. Thats 67% not 75%. You are forgetting
that between nodes, the packet has to be uploaded _and_ downloaded again
(both things cost bandwidth).

With regards to reducing the number of hops i agree with Andrew about
using something else than Tor.

-- 
Regards
Georg Sluyterman
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