FTP doesn't have any sliding-windows stuff built in, that's part of TCPYou're right of course. I think I was assuming that on a single monolithic FTP transfer, the window size will grow to a large value and stay there for the rest of the transfer. But BT transfers are typically lots of short-lived connections that open and close.
Hm, that would depend on your swarm. I haven't checked with wireshark/whatever, but I've watched connection stats of �torrent and rtorrent - and I generally stay connected to (and grab numerous chunks from) a handful of high-speed peers... which also means no TCP new-connection 3-way handshake and window size negotiation.
With FTP, you get a new connection for every file transferred, making it absolutely suck
if you're dealing with multiple smaller files. Torrents are bundled up into chunks, and don't suffer from this problem.
In any case, the point that BT simply externalizes the bandwidth costs so that it's borne by other parties (consumers or ISPs) is true regardless.
True, at least that's how it's being (ab)used right now.
It's a shame people don't put torrent technology to better use... the times I've tried grabbing a linux distro via torrents, I've had abysmally low speeds, since the university/whatever servers hosting ISOs via http/ftp don't participate. So instead of doing a little load-balancing, I always end up hitting a single http server for 20mbit/s instead.
OTOH, torrents aren't really suitable for "cherry-picking" files from a FTP server, it only really works when you'll be grabbing rather large packs of data. Sure, most torrent clients will let you only download partical contents of a torrent, but there's some waste involved in doing this, and the "workflow" for doing this isn't as easy as queueing files in a ftp client.
So, in summary, yes, torrents are a great idea. But even today, it's still only used by the computer savvy. The majority of regular people still don't use torrent. I know people will disagree with me, but it's true.
Not everybody playing World Of Warcraft are computer-savvy