Linux – iptables to throttle/slow down P2P

I'm not sure how interested you are in reconfiguring your entire setup (i.e., replace Debian), or how feasible it would be to place something like this behind your gateway, but FreeBSD has a feature in ipfw known as dummynet. Since it sounds like you don't feel like getting a dedicated hardware traffic shaper, this may be an option for you. We currently use it to choke SMTP traffic inbound and outbound through one of our proxy gateways to keep an aging NFS backend system from being overwhelmed and subsequently becoming unresponsive.

With some scripting and intelligent configuration of your rulesets, it would be feasible to be able to traffic control thousands of individual IP addresses.

What you're looking for is called Traffic Shaping. The best source of information for it (that I know of) is Linux Advanced Routing and Traffic Control. It's a little bit dated, but still has a ton of good information. If you google for Linux Traffic Shaping, you can find some scripts and tools to make the traffic shaping configuration a little bit easier.

The specific commands you will use, unless you find a tool or script to do the work for you, are tc and/or tcng. I also want to warn you that traffic shaping can get very complicated if you haven't done it before, particularly if you're trying to do it by hand.

Additionally, also remember that you can only reliably control the speed of data that you are sending out.

You might also want to check out these similar serverfault questions:

• Shaping Outbound Traffic to Control Download Speeds with Linux
• Linux Traffic Shaping Using tc
• Traffic Shaping Using tc
• Are there simpler ways to do traffic shaping in linux besides tc