See The Register for my analysis of the latest tweak in Bittorrent:
Gamers, VoIP and video conference users beware. The leading BitTorrent software authors have declared war on you – and any users wanting to wring high performance out of their networks. A key design change in the P2P application promises to make the headaches faced by ISPs so far look like a party game. So what’s happened, and why does it matter?
Upset about Bell Canadaâ€™s system for allocating bandwidth fairly among internet users, the developers of the uTorrent P2P application have decided to make the UDP protocol the default transport protocol for file transfers. BitTorrent implementations have long used UDP to exchange tracker information â€“ the addresses of the computers where files could be found â€“ but the new release uses it in preference to TCP for the actual transfer of files. The implications of this change are enormous.
As BitTorrent implementations follow uTorrentâ€™s lead â€“ and they will, since uTorrent is owned by BitTorrent Inc, and is regarded as the canonical implementation â€“ the burden of reducing network load during periods of congestion will shift to the remaining TCP uses, the most important of which are web browsing and video streaming.
Several commentors are upset with the article, mostly because ISPs don’t provide them with unlimited bandwidth. There’s not much I can do for those folks.
A few others claim that BitTorrent over UDP has a congestion control algorithm which they feel is in some way equivalent to the TCP algorithm, but this argument is flawed on a couple of levels. For one, many routers have tweaks in their discard logic that prefers UDP over TCP. This is a key problem with the widespread use of UDP for purposes other than those for which it was intended.
UPDATE: The explicit goal of this new tweak is actually to create a more friendly variant of the existing TCP congestion avoidance algorithm, and it was the pirates at Broadband Reports who said otherwise.
What remains to be seen, however, is what the actual effects will be in large-scale deployment, and whether the genie can be forced back in the bottle if they’re undesirable.
UPDATE 2: I’ve added “Alarming Title” to the title. This piece is getting a lot of people excited.