Richard Bennett: Was incorrect, Still incorrect, Always incorrect
> BitTorrent [gets its performance boost] as a direct
> consequence of its scalability, by running dozens
> (or even hundreds) of TCP streams concurrently.
For each swarm, BitTorrent only uploads to 3-4 streams at any given time, out of somewhere around 40 streams that it establishes. The remaining streams are dormant and nearly silent. Using CATV-Internet, the low upload allocation given all customers normally permits no more than two or three active swarms at any given time. These fact breaks your next assumption ...
> The proliferation of streams gives BitTorrent
> immunity, at least partially, from the Internet's
> packet-drop-triggered congestion management system.
Given that you have set your readers up to believe that BitTorrent is actively exchanging data at a high rate of speed over dozens or hundreds of connections, your readers might accept your untested, unproven assumption as fact.
The truth is that anywhere from 3 to 12 of those streams will be actively uploading at any one time. The dozens (not hundreds) of other streams are quite silent and are not contributing to any congestion. The "packet-drop-triggered congestion management system," therefore, only needs to quell 3 to 12 streams and this works very effectively.
Evidence that this works can be found in the hundreds of daily posts on BitTorrent support boards from users who have mis-configured their clients and try to upload faster than their own modems can handle. Because of the "packet-drop-triggered congestion management system," they achieve poor upload AND DOWNLOAD speeds, owing to the fact that dropped outgoing ACK and REQUEST packets are causing delays and retransmissions.
> By contrast, most Internet traffic moving upstream on
> residential broadband networks comes from applications
> with no more than one stream active at a time.
This claim is not only unsubstantiated, it is incorrect in any manner that you might try to consider it.
If you are talking about "Most" as in surfing (http requests), then most internet traffic comes from web browsers -- often 2 simultaneous connections PER SERVER. Due to advertising, most pages are made up from resources on multiple servers. This comments page draws advertising, images, code, and content from five (5) servers. Loading this page opens 10, not one but 10, simultaneous streams making HTTP requests.
If "most" means the amount of upload traffic, then most of that comes from BitTorrent P2P. As I said above, this will consume 3-4 active streams per swarm, and someone would normally operate 1-3 swarms at a time.
These facts completely invalidate your argument, as any packet-drop-triggered congestion management would quell BitTorrent's 3-12 upload streams AT LEAST just as well as it would a web browser's approximately 10 upload streams.
You seriously need to stop spouting this defective argument . It is like an addiction. So any time you hear yourself saying "hundreds of connections," please snap a rubberband that you keep around your wrist until this unwanted habit goes away.