Hello, welcome back to your free training for windows 7 courtesy of IT Free Training.
In this video I will look at USB and configuring USB devices using group policy. Before I have
a look at how to monitor the bandwidth and power needs of USB, it's pays to understand
a little bit more about USB. Currently there are four different standards
of USB. The first widely used standard was 1 point 0. This did have a few problems, mostly
relating to using USB hubs and was replaced by the 1 point 1 standard. Both standards
work at a maximum speed of 12 Mega bits per second. This is good for mice and keyboard
like devices, but not suitable for any device that requires high speed like hard disks.
The next standard released was USB 2 point 0 which addressed some of the sort coming
of USB 1. The maximum speed increased to 480 Mega bits which allowed it to be used for
devices like hard disks and video cameras. Previously USB was not fast enough for these
devices. In some case even USB 2 point 0 was not fast enough and people used anther standard
called fire wire to perform high speed transfers. Having said that, USB 3 point 0 is now available
running up to 5 Giga bits a second. Regardless of what devices you buy, when you plug in
the USB device your computer or USB hub will work out the speed of the device and match
the speed. In otherworld's, you could plug in a USB 1 point 1 device into a USB 3 point
0 port and the speed will automatically drop down to USB 1.
When you look in the device manager there are a lot of device drivers which make USB
work. The names of the drivers may change from system to system and operating system
to operating system. Open host controller interface is used for
USB 1. Enhanced host controller interface is used for USB 2 and extensible host controller
interface is used for USB 3. This is the driver that windows uses to communicate with USB
hardware in your computer. Opening device manager and looking for this driver is one
way you can determine which standard of USB your system supports. Depending on the hardware
on your computer the name of the device driver may change. Also if you have multiple USB
controllers in your computer you may see more than one device driver.
Your system will then install a number of USB root hub drivers. One for each USB port
on your computer. In this example, the first USB port is connected to a USB modem. When
you look in the properties for one of the USB root hubs you will see the modem.
The second device is connected to a USB D V D drive which will also be connected to
a separate USB root hub driver. The 3rd USB root hub driver is connected to a USB hub.
This USB hub can have it's own power supply, otherwise it will gets it power from the computer.
If you put in to many devices on the USB hub it may draw too much power from the system.
If this occurs, windows may not be able to use some of your USB drives. Let's have a
look at the device manager in windows 7 and see how all the USB drivers work together.
First of all, I need to open the device manager. To do this, open the control panel and go
to system and security and then under system select device manager. If I now go to universal
serial bus controllers, you can see there a lot of device drivers that make USB work.
You can see here the standard Open H C D USB host controller. This device is used for USB
1 devices. The driver above this, standard enhanced P C I to USB host controller is used
for USB 2 devices. If either of these drivers are missing your computer either does not
support that standard of USB or it is not configured correctly.
On some systems the name of these drivers may change so don't worry too much if you
can't see these drivers on your system. Also some systems have multiple USB controllers
so you may see more than one of these device drivers.
Down the bottom I have a USB root hub driver. Each USB port on the computer will have its
own USB root Hub. If I go to the properties of this driver and then select the power tab
you can find out what sort power needs this port has. At the top it says the hub is self
powered. In this case it means the power is coming from the computer.
Below this you can see that the power per port is 500 miliampre. This is a little miss
leading because as you can see down the bottom there is one device plug in and 7 free ports.
The USB thumb drive plugged into the computer is using the port and 200 millampre's of power.
If I was to plug a USB hub into this port, I could run 8 ports off that hub. In simple
language it is saying, this port can support 8 devices with 500 millampre for each device.
If I go to the advanced tab I can see the device is running at high speed. If I plugged
a USB 1 device into this port, this would cause this port to switch down to USB 1 speed.
If I go back to device manager, you can see anther USB root hub. This is for anther device
plugged into the system. If you want to find which USB root hub your device is plugged
into, it is a matter of trial and error to you find that right one.
On this system I have a USB hub plugged into the computer. You can see this has appeared
as generic USB hub. If I go into the properties for this device you can see that you have
a lot of the same options that I had on the other device driver. On the power tab you
can see how many USB devices are plugged into this hub.
At the top you can see that the hub is powered by the bus and that there are 100 miliampre
available for each USB device. In the attached devices section, there are 3 devices connected
to this hub. Listed also is the amount of power each device is using.
If I go to the advanced tab, I can see this hub is operating at high speed. Below this
I can see this hub has a single transaction translator or T T. When you plug a USB 1 device
into a USB 2 hub, the device must change the single from USB 1 to USB 2. The T T performs
this, without a T T the whole hub must switch down to USB 1. This USB hub has 8 ports. Even
with only one T T I can still plug as many USB 1 devices as I like into the hub. The
disadvantage of this is that all the devices must share the single T T which can cause
the performance of the hub to drop. This is only a problem if you have more than one USB
1 device plugged into this hub. A better quality hub has more T T's and thus the work load
converting from USB 1 to USB 2 is shared between them.
Down the bottom you can again see how many devices are plugged into the USB hub. This
time however you get an indication of how much bandwidth each USB device is using.
If I now go back to device manager there are still a few more USB device drivers. On this
system there are two composite devices and a mass storage device. These are required
for the operating system to communicate with the devices. Depending on which device you
plug in will determine which additional device drivers are installed.
Now that I have looked at how to install and troubleshoot device drivers, you may want
to put some controller on what users can do using group policy. If I now close the device
manager and open group policy from the start menu by typing group and selecting edit local
group policy, I can change the local group policy settings on this computer.
The majority of the settings can be found in computer configuration, administrative
templates, system and then device installation. These settings determine how device drivers
will be installed on your system. There are a lot of settings you can configure.
If you want to have device drivers installed with as little user interaction as possible,
you may want to configure turn off balloons when found new hardware. You can also configure
if windows will sent error reports to Microsoft. This kind of information does help Microsoft
improve their operating system, but some companies are sensitive about information that gets
sent out. If I go into the folder device installation
restriction I can control which device drivers are installed on the system. If you do decide
to configure options in here, you may want to consider settings the first option, allow
administrators to override device installation restriction polices. This will allow an administrator
to log into a computer and install a device driver regardless of what the settings are
set to, but will prevent the average user from doing this.
There are also options to allow you to customize messages that are displayed to the end user.
For example, you may want to display a message saying driver installation blocked, please
contact your helpdesk. Further down you have the option to prevent installation of devices
that match any of these device ID's. If I go into this policy and enable it and
press the show button, I can enter in the hardware ID's of the devices that I want to
prevent installation of. To get the device ID, I need to go back into device manager
and find the device I want to block. In this case I will block installation of
the coms port. If I go into the properties of com port 1 and then to the details tab
I can select the properties for hardware ID. You can see here that there are two values
present. Some devices will have multiple values and
it is important to get the right one. For example, if I was looking at the keyboard,
the keyboard would have an ID for the device and also one for human interface device. If
I were to copy the human interface I would block all input devices. Probably not the
result you wanted. In this case I want to block all com ports
so I can copy the second hardware ID. Now all I need to do is go back into group policy
and paste the value in and close the setting. If you want to try and prevent data being
removed from your network, you can also configure the option prevent installation of removable
devices. This will stop the user being able to use USB thumb drives.
There are also two more settings under driver installation. Now that I have finished configuring
group policy, if I now go back into device manger you can see that nothing has changed.
This is because the policy I set only comes into effect when the driver is installed.
If I un install com port 1 and then scan for hardware changes, you will notice that the
com port will be installed but this time it will appear under unknown devices.
If I go into the properties of the device, you can see that there is a message saying
the installation of this device has been blocked by group policy. That's it for USB and group
policy with device manager. In the next video I will look at application compatibility in
windows 7.