[drdaeman]

There were issues specific to BitTorrent. In particular, early uTP versions caused a lot of grief, as they had broken congestion control, which led to absurdly high PPS. Also, it hadn't worked well on congested WiFi hotspots. We had to drop UDP traffic having certain signatures, just to keep the network alive. This was a single one-time incident, though, not a general issue.

Either way, P2P traffic, compared to the unicast one, is also a bit harder for hardware to handle, as there are more connections with different peers. Not an excuse or anything - good ISPs are meant to deal with whatever kind of traffic their customers want to generate (unless it's broken/misbehaving or malware-infested systems), just saying that the load is of a slightly different kind.

-----

Actually, some ISPs I've heard about were setting up BitTorrent caches. They had set up `retracker.local` systems that some fairly large public trackers had supported, grabbed stats to see what's hot, and spawned seedboxes (serving internal customers only) for the frequently downloaded content. Legal waiver was this was fully automated, and working exactly like any other caching proxy, blah blah - given it was in Russia, no one cared anyway. This was quite nice optimization, that allowed to cut outside traffic, IIRC, up to 2-3 times while actually improving customers' experience.