[bittorrent] Choking based on network closeness?

Bill McGonigle bill at bfccomputing.com
Tue Jul 12 12:41:51 EDT 2005


On Jul 11, 2005, at 16:28, Brian Dessent wrote:

> Suppose peer A is right down the street
> from me on the same ISP but has his upload throttled very low, and peer
> B is thousands of miles away (lets say, Sweden, for the sake of
> argument) with a fat pipe and generous limits.  In terms of what's best
> for the host, it should choke peer A and reciprocate as much as 
> possible
> with B.

OK, this is a good example of a worst-case scenario for a 
network-closeness-only choking algorithm, but that's not what I'm 
advocating.  As I mentioned in my original message either a heuristic 
or a user-controlled knob would need to be set to determine when to 
favor the closer peers.

Take the scenario you outline, for instance.  Now set the upload speed 
on the peer down the street from you to 500k/s and the peer in Sweden 
to 505k/s.  Does it still make sense to go to Sweden for that extra 
5k/s?

If the only decision criteria is 'how fast can I get that file', it 
makes sense to go to Sweden.  If you value other things like 
efficiency, the cost of your Internet access bill, how major ISP's feel 
about the Bittorrent protocol, etc., then you may decide it's better to 
give up that 5k/s.

-Bill
-----
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