Modular QoS Command-Line Interface

As the Cisco QoS tools evolved, they became increasingly platform idiosyncratic. Commands that worked on one platform wouldn’t quite work on another, and there were always platform-specific requirements and constraints that had to be kept in mind. These idiosyncrasies made deploying QoS a laborious and often frustrating exercise, especially when deploying networkwide QoS policies, such as required by TelePresence. As an attempt to make QoS more consistent across platforms, Cisco introduced the MQC, which is a consistent, cross-platform command syntax for QoS.

Any QoS policy requires at least three elements:

1. Identification of what traffic the policy is to be applied to
2. What actions should be applied to the identified traffic
3. Where (that is, which interface) should these policies be applied, and in which direction

To correspond to these required elements, MQC has three main parts:

1. One or more class maps that identify what traffic the policies are to be applied to
2. A policy map that details the QoS actions that are to be applied to each class of identified traffic
3. A service policy statement that attaches the policy to specific interfaces and specifies the direction (input or output) that the policy is to be applied

As you see in the examples throughout this chapter, although the syntax of MQC might seem simple enough, it allows for nearly every type of QoS policy to be expressed within it and allows these policies, for the most part, to be portable across platforms.