Get the best out of your bandwidth with tc

Control Freak

Article from ADMIN 10/2012

By Chris Binnie

If you're looking for a way to make the most of available bandwidth, we'll show you how to throttle and shape traffic with tc.

System admins have many legitimate reasons for wanting to restrict the bandwidth allocated to a user or service. Bandwidth is still a finite and relatively expensive resource, even on today's Internet. The good news is that Linux provides a formidable bandwidth throttling solution that is hard to ignore.

With the ability to control bandwidth on routers, servers, and desktops, this solution is certainly fit for the purpose – especially because commercial alternatives, usually bolted-on or bundled with other proprietary operating systems, can cost significant money to implement. In some cases, these commercial solutions don't even perform well under load, incorrectly allocating bandwidth to one service or user at the detriment of the others using the network.

Before I get too carried away here, let me state that the Linux solution I'm referring to isn't for the faint-hearted. In fact, I'd go as far as to say that anybody who isn't blessed with an abundance of technical chutzpah might be better off looking away now.

That said, if you are up for the challenge, in this article I'll provide some working examples for you to experiment with, and I'll give you a glimpse into the inner workings of this solution. Supporting documentation can be found online, starting with the Linux Advanced Routing and Traffic Control website [1].

Ladies and Gentlemen

Traffic Control abbreviates nicely to tc. The man page for tc describes what it does beautifully (paraphrased for the sake of simplicity): Tc is used to configure Traffic Control in the Linux kernel . Features include:

Shaping – When traffic is shaped, its rate of transmission is under control. Shaping can be used to do more than lowering the available bandwidth – it can also be used to smooth out bursts in traffic for better network behavior. Shaping occurs

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