Sunday, October 2, 2011

The Beginner’s Guide to Using QoS (Quality of Service) on Your Router


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We’ve covered QoS before when we showed you prioritize your DD-WRT router’s traffic and in our 5th tip for getting the most out of Tomato. It’s a little more complicated than creating rules, so let’s see how things work.

What Is QoS?

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QoS, or Quality of Service, is a method for controlling traffic priority on networks. It works on all levels of network activity, but for our purposes, it’ll be centered around your home router. There, QoS kicks in when there’s a bottleneck and decides which traffic is more important than the rest. Exactly what is more important then the rest is based on rules that you supply. You can specify importance based on criteria such as IP address, MAC address, and even service name.

Where’s the Bottleneck?

Many people set up QoS hoping that it’ll do a lot of good only to report later that it doesn’t do anything. That’s because QoS only works when the bottleneck is in the right place, and the key settings are your bandwidth declarations.
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Suppose that your QoS settings are set beyond the bandwidth you receive from your ISP. What happens is that the traffic that leaves your router isn’t prioritized because your router thinks that there’s ample bandwidth available. Meanwhile, you’re hitting your ISP’s caps, and they’re the ones who decide what is and isn’t important.
On the other hand, if you set your QoS’s declared bandwidth lower than your allotted ISP bandwidth, you’re creating an artificial bottleneck where you can control it: at your router. Now, your own QoS settings kick in and re-arrange your traffic. The cost of bandwidth is pretty minimal, but by tweaking things slowly you can marginalize it further.

Tweaking Steadily

The key to getting your bandwidth back is tweaking and observing over time. The Uplink and Downlink settings are your keys.
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Start by taking a bandwidth test to find out what your normal speeds are from your ISP. There are numerous tests out there, such as Speakeasy Speed Test and SpeedTest.net.
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We suggest you start your QoS dabbling by setting these values to 85% to ensure that your QoS is being effective. Once you tweak your settings until things work the way you want them, you need to take the next step and ramp things up bit by bit.
Take your Downlink and Uplink and boost them by 1-2% at a time, preferably while maxing out your bandwidth and checking your QoS settings to make sure they’re still in effect. It’s possible to go as high as 95% percent and still have your bandwidth prioritization working. Kick things up by an increment and give it a few days. Lather, rinse, repeat. You can reclaim quite a bit of sacrificed bandwidth this way