Practical Technology

Chances are, everyone on your intranet has Gigabit Ethernet, with its 1,000 Mbps (Megabit per second) speeds. Or perhaps your laptop users are moving up to 802.11n Wi-Fi with 100Mbps throughput. That’s all great — but once your users hit the router, they’re all back to fighting over your far-more limited Internet connection (say, a 44.6 Mbps T3 line). That’s where traffic management comes in.

There are many ways to make sure your YouTube fans don’t eat up your Internet bandwidth. For example, Extreme Network switches, F5 Networks’ BIG-IP network traffic managers, and many other high-end network devices can help you get a grip on how much unnecessary traffic goes to the Internet. But, now Microsoft has built in a new, easy way to manage network traffic in Windows 7 and Windows Server 2008 R2: URL Quality of Service (QoS)-based traffic management.

Windows has long had QoS traffic management that used applications, IP addresses, and port numbers to determine which traffic got priority. Now you can set priority by website address. This way, all a network administrator need do is set up policies by website, instead of digging around for IP addresses, which may change over time. So, for example, you could set the Wall Street Journal’s site to have a high-priority while locking down ESPN.

To do this, you first set up a QoS Policy on Server 2008 R2. The simplest way to do this is to use the GPMC (Group Policy Management Console).

The key technology that makes all this work is Differentiated Services Code Points (DSCP). This is derived from an Internet networking standard, RFC-2474, that defines how a value in a TCP/IP packet header is set. It’s used to determine how high a priority packets are given as they make their way around a network. Generally speaking, the higher the DSCP value you give a site, the higher its traffic priority is. So, for example, if you gave a company external site a DSCP of 63 — the scale ranges from 0 to 63 — traffic to that site will be much faster than to, say, YouTube with a DSCP of 0.

Exactly how the traffic is throttled to a given site isn’t determined just by its DSCP. You have to set in the GPMC how fast or slow a site’s traffic is permitted in either KiloBytes per second (KBps) or MegaBytes per second (MBps).

Once you set up your DSCP values and their corresponding throttle rates on the Policy Profile tab, you can assign them to URLs. These URLs can include wild-card characters and — although you won’t need to for most websites since they use port 80 by default — you can also specify a port number. You’ll also want to select the Include subdirectories and files check box to apply the traffic management settings to all of the URLs’ subdirectories and files.

There can be competition between policies. The tie-breakers start with DSCP, and then (from highest to lowest) are determined by host name listing order, IPv6 address, IPv4 address, and wild-card. So, when you build your policy, be sure to list the most mission-critical sites first by their specific URLs.

To make sure your policies work the way you want, Microsoft provides a handy QoS Traffic Generator, and examples on how to use it with its QoS Traffic Generator Example Usage.

That’s pretty much it on the server side. On the Windows 7 client side all you need to do is click a few buttons and you’ll be on your way. Click Start -> Control Panel -> Network and Sharing Center. Once there, select the appropriate LAN connection. Then, once you’re at the Local Area Connection Status window, click on Properties, make sure the QoS Packet Scheduler radio button is clicked on, and you’re in business.

Sure, other network tools give you even finer control, but for a pre-packaged network traffic management solution, QoS URL is a very handy and easy to use addition to the Windows networking family.

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