[BitTorrent] Bittorrent choking itself?

Olaf van der Spek OvdSpek at LIACS.NL
Wed Nov 17 10:53:40 EST 2004

fenixoblodra wrote:
> Recently while discussing an old problem I was having with a
> bittorrent implementation (I posted here and got a few ideas a long
> while back, which helped somewhat but not entirely) someone posed the
> idea that, if left to its own devices, BT is capable of choking a
> connection by sheer volume of inbound and outbound requests.  I found
> this somewhat odd considering in my previous tests both the BT client
> and the windows bandwith monitor showed that the network wasn't
> anywhere close to being utilized. However I decided to give the idea a
> shot---in essence what was done was to take a 3rd party client
> (Torrentstorm in this case) and rather than leave it set on
> "Unlimited" upload, set it to an arbitrary speed higher than my
> upstream bandwith
> What I saw was that, despite the fact that the actual upload rate
> failed to change, the download rate typically jumped (I tried this on
> a few torrents) and on average I seemed to reach a higher download
> rate with unlimited upload off regardless of the rate that I was
> uploading.
> Might there be anything to this idea? I realize without running
> controlled tests on a LAN where i can see all the variables it's
> somewhat anecotal evidence but it seemed to make consistent results
> across BT installs on several different machines.  I had the idea that
> maybe it's not so much the BT client or the connection but rather the
> local switching software (IE the router or DSL modem) which chokes on
> handling the requests...but I'm not sure how one woould go about
> verifying this

It's related to TCP rate control, congestion, queue lengths and router 
drop policies.
Probably not with BT requests.

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