Network Security Principles and Practices

Overview of CAR

CAR is a QoS mechanism that also lends itself to use in security implementations. CAR's primary function is to control the amount of traffic flowing through an interface based on various configured parameters. CAR can perform two basic functions:

• Bandwidth management

• Traffic classification for use by other QoS mechanisms

This chapter concentrates on CAR's first function—bandwidth management on a router.

CAR uses rate limit definitions to control the traffic flowing through an interface. CAR uses three main criteria to perform bandwidth management:

• Average rate— Determines the long-term average transmission rate.

• Normal burst size— Determines how large traffic bursts can be before some traffic exceeds the rate limit.

• Excess burst ...