"That puts Netflix above HTTP websites (18 percent), BitTorrent (11 percent), and YouTube (10 percent) as a source of downstream traffic during peak times in North America. (BitTorrent still accounts for half of all upstream traffic)"
I don't understand this -- surely every downstream requires a corresponding upstream? Are they only counting upstream from domestic users? Or is the vast majority of bittorrent traffic to american users coming from seeders outside the US?
They are counting only at one end -- in this case, the client. So, traffic inbound/outbound from commodity ISPs. The traffic leaving servers is not typically considered "upstream".
With HTTP and media streaming you send very little data ("I'd like this web page, please") and you receive lots ("here's the entire content of the web page"). With BitTorrent you send lots of data (fragments of files to other peers) and you receive lots (the fragments of files you're missing).
With HTTP you still send an ACK for every incoming packet. A friend of mine at university was the technically minded person at his fraternity, and he found that just the outgoing ACK:s were saturating the DSL line.
Media streaming might be done over UDP, depending on the protocol, which should alleviate this a bit.
You can send a HTTP Get Request which is an upstream traffic less than a KB, and get back 100KB in data (downstream). Torrents where users have a 1:1 seed ratio, will ideally have 100KB upstream for every 100KB downstream.
Downstream has a higher total volume than upstream. (Case in point, Netflix.) 11% of downstream and half of upstream may represent the same absolute bandwidth.
I don't understand this -- surely every downstream requires a corresponding upstream? Are they only counting upstream from domestic users? Or is the vast majority of bittorrent traffic to american users coming from seeders outside the US?