Summary: It's possible, even easy, to monitor the amount of bandwidth a computer is using. It's much more difficult to control.
I have 3 kids, each has his own computer, I have a laptop, and we are all sharing an ADSL connection. Sometimes one of the kids hogs the network and everybody else does not get any bandwidth. And I sometimes want to lockout one of the kids from the internet so he will turn to other activities ... such as his homework.
There's good news and there's bad news.
Bandwidth is a lot like having kids: monitoring is easier than controlling.
•
Let's start out with the good news. The ability to monitor your network and a lot of other items is built in to Windows XP, Windows 2000, and Windows NT in something called "Performance Monitor".
Run performance monitor by pressing Start, selecting Run, typing "perfmon" and pressing OK. You should get something that looks somewhat like this:

Right click in the empty chart area and select Add Counters... and you should see something like this:

The Performance Object dropdown lists several objects on your computer whose performance can be measured. The Processor, for example, is one. In that list select Network Interface, and the result looks like this:

The first list at the bottom of the dialog allows you to select which counters relating to that object you want to monitor. The second list allows you to select which object if there are more than one. In this example we'll select my "Intel Pro" network card on the right, and "Bytes Total/Sec" on the left. Press Add and Close and you'll see perfmon start to report the total bytes traversing the network card over time. After a little while in my example, it looks like this:

Perfmon is an incredibly powerful monitoring tool. There are lots of things available to monitor, and many display options. I encourage you to play around with it some.
Of special note is the Select Counters from Computer option in the Add Counters dialog above. Perfmon allows you to monitor the performance of another Windows XP, 2000 or NT computer remotely, across your LAN. This means, for example, if someone on your network is hogging all the bandwidth then you can monitor each machine remotely in real time to see just who that might be.
Monitoring is fairly easy. In addition to Perfmon there are certainly many third party applications that will allow you to do the same with different display and even triggered actions.
Control, on the other hand, is the bad news. True control of something shared like a DSL connection can be done, but it gets costly. It's typically performed by high end routers that allow you to specify, often in great detail, how the bandwidth should be allocated or prioritized. Unfortunately that's usually out of reach of the most home LANs.
In all honesty if this were my situation I'd just make sure the router was in arms-reach of my desk, and the cables well labeled. Then I'd physically unplug the connection for any computers who's users I felt needed to spend more time in the "real world".
But that's just me.
Related Links:
Article C1950 - May 26, 2004
I visited a web page that showed percent of bandwith used at the top. I would like to add something like that to my site, but have been looking for hours and now am posting here. Do I need to have a router that logs that info ? I don't.
Posted by: Dan Schwartz at June 18, 2006 8:47 AMOf special note is the Select Counters from Computer option in the Add Counters dialog above. Perfmon allows you to monitor the performance of another Windows XP, 2000 or NT computer remotely, across your LAN. This means, for example, if someone on your network is hogging all the bandwidth then you can monitor each machine remotely in real time to see just who that might be HOW DO THIS WORK?
Posted by: SCHALK at May 28, 2007 6:51 AMThanks, very descriptive and helpful information that you posted.
Posted by: Christian at July 18, 2007 1:27 PMI have found the perfect tool for controlling my kids time on the computer. It's called "Enuff". You can control exactly how much time on the computer and when and who, and even what, and it can all be controlled from your machine over a network. You pay for it once, but it really works well and is simple to use.
Posted by: Leo Hartas at February 21, 2008 2:34 AMIf you use DD-WRT as the firmware on your router then you can set up QoS (Quality of Service). See: http://www.dd-wrt.com/wiki/index.php/Quality_of_Service
I was having a problem with my son "hogging" all of our bandwidth with World of Warcraft, and his Xbox 360 live account, so I used QoS to limit the amount of bandwidth his computer and Xbox can use when there is a large load on my router.
DD-WRT is easy to setup on a Linksys WRT54G, or a Netgear WGR614L.
Posted by: Emory Lehman at September 24, 2008 6:12 PMI followed the instructions but all i see is the network card (intel[R] Pro....) and the other option aswell. That network card is my one and i cannot see any other computers even though there are 2 other computers connected to the same router. Plz help
Posted by: Shane at October 13, 2008 11:58 PMI am using XP with SP3,on running perfmon...under PERFORMANCE OBJECT no drop down is available....why so?
Posted by: Prince at December 11, 2008 1:29 AMplease sent me how to manage bandwith size
Posted by: Pratik A Shah at March 6, 2009 11:22 PMYou need a bandwidth monitoring software.
Posted by: WFilter at April 21, 2009 7:00 PMI recommend "WFilter", which can monitor email/web/bandwidth/ftp/messenger.
You can also deploy a network appliance from eTelemetry called Metron SE on your home or office network...
http://www.etelemetry.com/products/metronse.aspx
Posted by: Jim at October 21, 2009 10:22 AM