Is Windows really reserving 20% of your band width?

[Digger[NJLP]]

Applies to Windows XP Pro and above!!!!

Well, after seeing the post on the Digg.com site I decided to confirm the story. I read a few posts on different forums about the QoS Group Policy setting to reserver 20% of the bandwidth for QoS traffic.

QoS traffic is used by tools such as "net send" and internal windows tools used to discover network presence. Companies that write networking specific software can use the QoS tools to confirm presence of servers, clients, port checking, etc.

Microsoft inserted a Group Policy to reserve 20% of your bandwidth for supporting these QoS packets.

Read Quote directly from the GP editor in Windows XP

Determines the percentage of connection bandwidth that the system can reserve. This value limits the combined bandwidth reservations of all programs running on the system.

By default, the Packet Scheduler limits the system to 20 percent of the bandwidth of a connection, but you can use this setting to override the default.

If you enable this setting, you can use the "Bandwidth limit" box to adjust the amount of bandwidth the system can reserve.

If you disable this setting or do not configure it, the system uses the default value of 20 percent of the connection.

Important: If a bandwidth limit is set for a particular network adapter in the registry, this setting is ignored when configuring that network adapter.

My advice is this:

If your PC is alone on your home network or has one or two PC's connected wirelessly.

If your PC connects to the internet via your cable/DSL router directly.

If you use dialup for your internet access

If you run a small home network with some simple standalone PC's acting as servers.

If you are running Linux/Unix servers and a few Windwos PC's

Set the 20% setting to 0 by following the below procedure.


The only other alternative is you're running a Windows Domain, as I am. If you are running that type of network you should know whether or not you need to reserver 20% of bandwidth for QoS packets.

I myself run a web server and that does not require any QoS tools and/or features, so I tweaked the GP setting. I have read that some VoiP routers and programs are starting to use QoS so you may want to read up on what your specific software uses.

Get back your 20% of bandwidth

1. Go to run and type gpedit.msc

2. Drill down the GP tree following the path Computer Configuration ->Administrative Templates ->Network->QoS Packet Scheduling

3. Under the QoS Packet Scheduling GP look for "Limit reservable bandwidth"

4. Enable it but set it to 0%

Close the GP window and to be safe reboot.

Q. Will this hurt my PC?

A. No, if you have a program or use a tool that utilizes QoS, the packets themselved will be sent out via the TCP/IP stack with the same priority as everything else. This just reserved 20% of the bandwidth so if it had to send out a packet associated with QoS it would use that 20% of reserved bandwidth and get out and back slightly quicker.

Here is the link to the Microsft Tech Net article explaining QoS and why/how to use it.

http://technet2.microsoft.com/WindowsSe ... x?mfr=true

Ack... That was a lot of typing..

[[FETT]Cupcake]

I checked my system for it. I didn't have "limit reserve bandwidth in there. Maybe x64 is diferent.

[Digger[NJLP]]

Really, I'll have to look at work tomorrow.
Hmm.. Is their anything in that GP container?

On my wife's XP Pro box and her's looks the same as mine downstairs. Does it look like this?

[[FETT]Cupcake]

Found it. Thanks.

[harlock]

Is there really a difference in speed with this option?

[Digger[NJLP]]

Well I have seen a few people post on the web their test of bandwidth before and after and it did show a difference.

But it really relies on what does it reserve and how much data do you really push over your internet connection.

I'm trying to find out if the QoS service itself looks for an internet connection and evaluates bandwidth or if it just reserves 20% of your nic's bandwidth.

Either way people who connect to the internet directly through their cable modem will benefit. Older cable modems, like my Motorola Surfboard, are using a 10 Mbps connection. That would be the bandwidth you have so Windows would thus allow you highest transfer rate of 8 Mbps per second.

I used the Performance monitor to monitor the network card. I loaded the bandwidth meter to have a reference point and it was solid at 11 Mbps, the speed of the wireless card I had in this laptop. I also loaded the meter for Total bytes sent and received per second on the network card. My first thought was most people would argue that if the bandwidth meter reads the nic card then that would be the bandwidth reserved with QoS. But QoS was developed to reserver bandwidth for tools and an attempt to provide packet messaging quality from one point to another. I should just quote the MicroDudes..

Category of QoS Mechanisms Description
Admission control
Determine which applications and users are entitled to network resources. These mechanisms specify how, when, and by whom network resources on a network segment (subnet) can be used.

Traffic control
Regulate data flows by classifying, scheduling, and marking packets based on priority and by shaping traffic (smoothing bursts of traffic by limiting the rate of flow). Traffic control mechanisms segregate traffic into service classes and control delivery to the network. The service class assigned to a traffic flow determines the QoS treatment the traffic receives.

So my thought is it may measure the bandwidth it observes by possibly pinging a Microsft server maybe?
Either way I'm speculating, so then I surfed the web.

At my highest my nic card was processing 657830 bytes per second. Multiply that by 8, since 8 bits in a byte, and you get 5,262,640 bits per second or 5.3 Mbps.
Ok so what was I doing, I had an MP3 streaming in from my server and I was downloading a 8 meg file from cnet at like 170 Kbps.

From that test alone I have not doubt that I can hit the 8.2 Mbps limitation set by the GP. Now with a 100 Mbps card it would be a lot harder.

But again if its not the bandwidth of the card, which I have yet to find out, and it is a test of bandwidth out through your WAN link it may be a much worth while tweak.

[Digger[NJLP]]

Well I had a post in the TechNet forum and after a few members pretty much saying the same thing, I was directed to this article..

http://support.microsoft.com/default.as ... -us;316666

This is the article on QoS and what it affects. After reading through it, I beleave its well worth the tweak. It appears that QoS is an API thats part of the TCP stack. And if the program sending that packet wants to use priority packet sending it would use the QoS features.

Foremost the QoS services first determines the rate of bandwidth to the destination network, how I don't know. And then determines how much of that bandwidth to reserve for the send of the priority packets.

So what it comes down to is how you connect..
Dial/Up
Yes tweak it
Broadband
Can't hurt unless you know you are using something that uses QoS.
Internal Lan Domain
I would probably say you need to determine the tweak yourself.

More info...
http://www.microsoft.com/technet/itsolu ... pip2k.mspx

This link takes you to the TechNet Article on the MS TCP/IP stack deployed with Windows 2000. It shows you where in the stack QoS API performs and even a flow chart showing how it wraps in to the rest of the stack.

I'm starting to get that sinking feeling that this is a tool written in to MS's stack and is one of those things "they" are using.

You never know it could be every packet sent to and from the controls for automatic upates uses QoS..

ack ack and more ack...