XP: Prevent QOS (Quality of Service) from Reserving Bandwidth

Contributor Icon Contributed by AlexTheBeast Date Icon December 8, 2003  
Tag Icon Tagged: Windows

Many people believe that the QOS changes to TCP/IP decrease your internet speed. This is how to change this.


Quality of Service (QOS) by default reserves 20% of your bandwidth. Superfically this sounds like you lose 20% of your bandwidth when QOS is enabled. QOS has been designed to ensure that certain programs that need a particular amount of bandwidth can reserve it.

If these bandwidth-demanding programs are not running, then QOS is not going to kick in and reserve this space. So relax! If this type of program is running, then you want to be able to give it all the bandwidth it needs.

For further discussion you can read the microsoft support article on this topic: http://support.microsoft.com/default.aspx?scid=kb;en-us;316666

Despite all of that, here’s the recipe…

Changing/Disabling the QOS in XP Pro:

1. Be sure that you are logged in as administrator
2. Select Run from the Start Menu
3. In the Open box type gpedit.msc and click OK
4. When the Group Policy Editor opens, double click computer configuration to expand
5. Double click administrative templates
6. Double click Network
7. Double click QoS Packet Scheduler
8. Double click Limit reservable bandwidth
9. Select the Setting Tab
10. Click the Enabled Option
11. Change to the Bandwidth limit % to whatever you wish it to be. You would change it to 0% to turn it off.
12. Click OK
13. Exit the Group Policy Editor
14. Reboot

I have searched for a registry edit for XP home and those particular registry keys are not in the Home version of XP.

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  • bob
    This is all a myth. Unless you are on an Active Directory domain with QoS enabled applications then it does nothing!
  • Anonymous
    If you read the recipe above, it appears that the original author agrees.
  • Anonymous
    By Microsoft

    "There have been claims in various published technical articles and newsgroup postings that Windows XP always reserves 20 percent of the available bandwidth for QoS. These claims are incorrect."

    also from Microsoft

    "By default, programs can reserve up to an aggregate bandwidth of 20 percent of the underlying link speed on each interface on an end computer. If the program that reserved the bandwidth is not sending sufficient data to use it, the unused part of the reserved bandwidth is available for other data flows on the same host.
    "
    This tech-recipes article is not true on QoS.
  • Anonymous
    Well, in engineering nothing is really true of false but built more around "use cases". From what I have read, this feature mearly balances the amount of bandwidth between application/connections on the local host. For example: you start to download 1 mp3 that is 3 meg. Then you start to another 1 meg mp3. In the old style WIN TCP stack (network connection) the majority of the band width is use by the first download while the second download uses only a little bandwidth needs to wait for the first to finish before it can increase it's connection capacity.

    In XP, the first connection will use 100% until the second is started. At that time the second download request starts, 20% or so of total bandwith is instantly allocated to the second program and after that a round robin (1-2-3-1-2-3-1-2-3-1-2-3) starts to occur giving slightly more band width to the application until things are equal.

    Microsofts technical white paper is just that, a technical document that not only mixes network engineering but all also client TCP stack design details. I think the people that made the recommendation to turn off QoS should probably brush up on their TCP/IP basics. The paper is very clear if you understand how TCP retransmission occurs it makes perfect sense.

    TCP is connection based protocol. In other words there is some checking that you get all the requested data. As the data streams to you, some times bits are lost along the way. This is generally called packet loss or just loss. Each packet has a number (1,2,3,4,5,6,7,8,9) so if a packet is missing the recieving side will ask for that packet number again 1,2,4,5,6,7,8.... Oh, can I have #3 again plase). We call this "retrans" (retransmission). In the first "old style" example the the first mp3 soaks up the bandwidth but the second does get a chance to make the request but lwill ose a few of the packets due to saturation caused by the first download. Retransmission occurs which means that even MORE traffic on the network which isn't a good thing.

    There are a lot more reasons why QoS in XP (and 2000) is a good thing. Disregard the artical and keep it turned on.
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