Class-based queuing
Aug 1, 2001 12:00 PM, BY STEVEN M. BLUMENFELD
At Lawrence Berkeley Laboratories the idea of class-based queuing (CBQ) was developed to better manage the growing bandwidth needs of enterprises. This bandwidth-management algorithm has been designed to better deliver appropriate, controllable service levels across IP networks.
Class-based queuing allows the network administrator to divide users into classes based on specific IP addresses, protocols or even applications. In a broadcast facility you could think of this as a class system for network machines, with the highest class going to production machines moving high-bandwidth graphics and the lowest class to e-mail and word processing.
Network administrators use CBQ to classify traffic into a hierarchy that reflects the policies of an enterprise. It also ensures that each traffic class has the appropriate quality of service.
CBQ integrates easily within an existing router network and provides more control and reduced bandwidth costs. Your administrator would configure a LAN-to-LAN network between the local network and selected WAN routers. This minimizes costs by eliminating the need for any hardware changes in the router network.
CBQ is an IP network layer bandwidth management tool that provides benefits across any Layer 2 technology and is effective with any IP protocol, such as TCP and UDP. CBQ uses standard TCP/IP flow control mechanisms to control end-to-end traffic so all TCP/IP stacks, whether client or server, can take advantage of it.
CBQ can be used to create different service levels that are strictly enforced. Each class is guaranteed access to a specific amount of bandwidth; a minimum guarantee. They also can borrow unused or idle bandwidth when they need to burst above their set minimums.
Each class can have its borrowing priority set for the most important uses, which gives it first right to any excess bandwidth. The class ranges also can be set to maximum available bandwidth — thereby shutting every other class down to zero, in which case the user gets best-effort service.
You should ask your network administrator if your facility is using CBQ or some variant of it. It will increase your network's effectiveness and help to keep your bandwidth costs down.
Steven M. Blumenfeld is currently the vice president of advanced services for America Online.
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