Networking

Prioritize network traffic with QoS policies to control bandwidth usage

Brien Posey goes over the basics of setting up QoS polices in Windows Server 2008 R2 that will allow you to prioritize latency-sensitive applications to make sure they always get the needed bandwidth.

Quality of Service (QoS) allows network administrators to prioritize certain types of network traffic and to ensure that latency-sensitive applications always receive the required amount of bandwidth. In order to prioritize traffic in this way, you must create a series of QoS policies.

Windows Server 2008 R2 allows you to create QoS policies at both the user and the computer level. Computer level policies remain in effect regardless of which user is logged in, while user level policies are user dependent.

To create a QoS policy, open the Group Policy Object Editor and then navigate through the console tree to Computer Configuration (or User Configuration) | Windows Settings | Policy-Based QoS. Next, right click on the Policy-Based QoS container and choose the Create New Policy command from the resulting shortcut menu. This will cause Windows to launch the Policy-Based QoS Wizard.

The Wizard's initial screen requires you to provide a name for the policy that you are creating and to specify an outbound throttle rate (in either Kbps or Mbps). You also have the option of specifying a DSCP value. The DSCP value refers to the Differentiated Services Code Point field that is used in the IP address header. This code is used to differentiate between different types of network traffic. Because the DSCP code is 6 bits in length, it is theoretically possible to classify up to 64 different types of traffic streams. However, most latency sensitive protocols already have associated DSCP codes.

When you click Next, the wizard will prompt you to specify which applications the policy should be applied to. You have the option of making the policy applicable to all applications or you can specify a specific application/ The wizard also gives you the option of applying the policy to a specific HTTP based application. To do so, you must simply provide the URL for the Web application that you want to throttle. This can be an internal or an external URL.

Once you have indicated which applications the new policy should apply to, click Next and the wizard will prompt you to enter source and destination IP address information. By the default, the policy applies to all source and destination IP addresses, but you have the option of specifying individual IP addresses or address ranges (prefixes). If you choose to specify an individual address or address prefix, you can use either IPv4 or IPv6 addressing.

Click Next, and you will be taken to the wizard's final screen. This screen asks you to specify the protocols and ports that the policy should apply to. For example, you might apply the policy solely to TCP packets that are using Port 80. Since some applications send traffic on one port and receive responses on another port, the wizard allows you to specify source and destination ports independently. You also have the option of specifying a port range. When you are done, click Finish to create the new QoS policy.

As you create QoS policies, it is important to remember that the policies will only be effective if your networking hardware is QoS aware. Of course ,Microsoft first introduced QoS over a decade ago in Windows 2000, so most newer networking hardware should not have any trouble with QoS throttling.

Related reading:

About

Brien Posey is a seven-time Microsoft MVP. He has written thousands of articles and written or contributed to dozens of books on a variety of IT subjects.

1 comments
lesko
lesko

Most larger shops have separate server groups and network groups and they tend to not trust each other so the trust boundary is at the switch or router where the packets are re-tagged. Most of the distrust started eons ago when MS decided to tag everything from IE a TOS of 5.