QoS stands for "Quality of Service" and can solve network speeds problems, particularly if you're using VOIP and / or P2P networks such as Bittorrent and / or Emule.

Why do I need QoS ?
QoS lets you prioritize your internet connections so not one service can take up all your internet speed.

Here's a bit of help and confirmation that it works Great with DD-WRT v23 firmware.

Most ISP's provide much higher downstream speeds than upstream speeds.  For example on Earthlink cable I have a 5 mbit download rate and a 512 kbit upload rate, so bit-torrents are far more likely to max-out my upstream bandwidth than they are my downstream bandwidth.

This also means that if you're downloading files, surfing will probably get slow, and streaming radio or VOIP phone calls get choppy and unusable.

There's a very easy to fix this with a WRT router running DD-WRT firmware.  For the sake of this discussion I'm assuming that you've already succeeded in getting your router running with the firmware, working with the documentation found: Here

You must first discover your real-world upload and download speeds.  You can measure them Here.

Also you might want to compare and take the average of the results you get there with those received from Here.

Next open up your web browser and go to the Router Webpage (http://192.168.1.1).  If yours router address is other go there instead,

Now click on the "Applications and Gaming" tab on the top then go to the sub-tab "QoS"

First select WAN (Wide Area Network) and not WAN-LAN.  I wanted to control data through the WAN and am not concerned about the data flow through my LAN Local Area Network, and it's likely you're trying to solve the same problem I was.

You must now setup bandwidth allocation:
 In my example on Earthlink Cable, I have approximately a 1500k download rate and a 300k upload rate.

The numbers requested are 80% of actual because of packet overhead. For each packet you send out the connection sends back a packet to make sure it came alright. This is called overhead. This number has to compensate for overhead. So I used 325 kbit which is actually ~ 70% lower then my actual upload. This is because I run utorrent all the time and because of all the connections needed, it uses a lot of overhead.

If you set this number too high your QoS won't work like it's supposed to so I recommend you use 80% of your current bandwidth, so if you had numbers like mine you would use (512 x 0.80) = 409.60 kbit.  Enter that for upload and see how it runs, then adjust from there.

Set your download rate as high as 95% of your measured download rate.  For me it was 5000K so I set mine to 4750.

Chances of you constantly maxing your download rate enough to saturate your line is very unlikely so use a ballpark estimate of from 90-95% of your download speed.

Once your done you can tweak your upload speed keeping in mind that lower is usually quicker - in a sense.

I found that the 80% wasn't good so going down in 25kbit intervals I found 325 seems to keep everything speedy. Of course yours might be different depending on your measured speeds - so you may want to ultimately adjust this critical figure within the range of 70% to 80% of your upload rate to see where it gets optimized.

If you aren't running internet playable games it's recommended you leave the "optimize for gaming" feature unchecked.  This is for specific games that support QoS, and if you're interested in this check the website for more info.

Next - there are some predefined services on the list so check through it and find one that says "http" when you click on it set it so it's on port 80 using TCP/UDP.

Once your done making changes click "Modify" and "Apply" at the bottom. This should set up http. Go through the list and setup your port ranges and services that are needed. Make sure you click modify when your done with each (or add if you created a new one). When your all done with that page and all your services are satisfactory then click "Apply" on the bottom. It should take you back to the QoS page.

Excellent your services are set, so now just find in the list all the services you want and click "Add"

Next set the priorities of those services setting Bulk (the lowest) and "Premium" (the highest)

Obviously you only set premium only to services which you want be fast all the time like http, gif, jpg, streaming audio, dhcp, dns, etc).  Note: because I have VOIP I added the entry labled "SIP" and set it to "Premium".

Make sure you set your P2P services to "Bulk" since one of the main purposes of QoS will be to cause those services to throttle back when your on the phone and critical VOIP packets are needed or you're surfing and http packets are needed.

When your all done with this click "save settings"

This should take a few seconds to get going again as the router has to restart some things.

Now if you have VOIP you can do what I did and install the MAC address for the SIP device in the area defined as "Mac Priority".  Add it and add the Mac address of your E-Mule / uTorrent computer (if one is so designated).  Then setup the MAC for the SIP to Premium and the MAC for the E-Mule / uTorrent machine to "Bulk".

I read that the port priority won't work except with older Linksys routers such as the 54G model, and since I had a GL I left all of those settings at premium and left everything else alone.

Next just go to the administration page, find and click the button that says "reboot the router".

See how it works.  Tweak things as needed, but if you followed these directions it should get you pretty excited since you'll be able to run E-Mule, and uTorrent and anything else you want to run - all the time without having wait for web pages or shut it down when you want to talk on the phone - which was a royal pain the butt.  If you've been there and done that, like I have for a long time, you're going to be very happy when you get this setup and working correctly.

Hooray for QoS service and DD-WRT firmware.   For additional info on QoS Click Here

Thanks.

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