[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: Reduce hops when privacy level allows to save Tor network bandwidth

* on the Tue, Nov 17, 2009 at 03:26:10PM +0100, Georg Sluyterman wrote:

>> 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).

All of that is wrong. You're assuming that Node1 transmitting to Node2
and Node2 receiving from Node1 are two separate streams. My "diagram"
has numbers where each transfer takes place. The first diagram has 4
transfers and the second diagram has 3 transfers.

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

People are going to use Tor even if they don't need strong anonymity
because it is free, and because it has certain desirable attributes
that other things such as VPNs don't give you. Given that they're
going to use Tor, why not minimise the amount of bandwidth they're
using in the process of doing so.

To unsubscribe, send an e-mail to majordomo@xxxxxxxxxxxxxx with
unsubscribe or-talk    in the body. http://archives.seul.org/or/talk/