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Limiting Bandwidth Hogs on Public Wireless Nets?
arglesnaf asks: "I'm a consultant and spend a lot of time on public wireless networks at client sites (mostly hospitals / universities), coffee shops, and hotels. Quite often, the problem is that some person is running BitTorrent and eating 100% of the bandwidth. The result is that I can't get email during the day or play World of Warcraft in the hotel. I have considered sniffing and spoofing TCP resets to free up some bandwidth but need an automated way to handle new BitTorrent connections. Does anybody have any ideas on how to automate the sniff and reset strategy, or other ways to carve out a little bandwidth from hogs on public wireless?"
Use OpenBSD as your gateway OS and set up queues so that BitTorrent is allowed on its well known ports, but carve out dedicated bandwidth as well for other services like imap, smtp, http, https, etc. to make sure they always have priority over torrents. You can prioritize the queues so that interactive services like ssh and http/https will pre-empt bandwidth from bulk transfer services like BitTorrent and ftp. The amount of control you have with pf is any geek's dream. You can even go so far as to say that hosts running Windows get put in a lower priority queue than hosts running anything else. :)
If you reduce your mtu, you might be able to squeeze some packets through and reduce latency. At least that is what I did when sharing a 56K modem connection. This also helps when your webbrowser is trying to download multiple images simultaneously.
Otherwise, go to Starbucks and pay $.10 cents a minute, because hardly anyone else will.
The excellent network attack package dsniff has a really cool utility tcpnice that may help.