Introduction

Delay. Limited bandwidth. Sensitive traffic. All of these issues and more have to be addressed on your network. Regardless of how much verbiage is used to describe it, you may find yourself facing a network situation where certain traffic has to be differentiated and given priority over all other traffic. Even more complicated is the deployment and management of multiple priorities. What scheme or mechanism will give you the ability to prioritize in the best way for your situation? There is much available, and you need to understand your options. All of these fall under the umbrella of quality of service (QoS)

QoS ensures that a minimum level of service will be provided to certain classes of traffic. By prioritizing, these techniques enable business-critical or delay-sensitive applications to operate properly in a congested network or in limited bandwidth environments.

There are three levels of QoS:

• Best effort Every possible attempt to deliver a packet to its destination is made. This service type carries no guarantees a packet will reach the destination.

• Integrated services Provides applications with a guaranteed level of service by negotiating network parameters end to end. Applications request the level of service necessary to operate properly and rely on the QoS mechanism to reserve the necessary network resources before the application begins its transmission.

• Differentiated services Differentiated service includes a set of classification tools and queuing mechanisms to provide certain protocols or applications with a certain priority over other network traffic. Differentiated services rely on the edge...