ystem. These include network processors, classification and forwarding processors, search engines, and switch fabrics. In this chapter, we turn our attention to the last important piece of this architectural jigsaw puzzle-ti managers. THE DEFINITION AND PURPOSE OF A TRAFFIC MANAGER In some networking realms, not all transmitted packets can be treated in the same way for profitabil- ity and efficiency reasons. As a result, different classes of service (CoS) must implement differenti- ated levels of quality of service (QoS) as expected for each packet that traverses the network. This QoS framework reflects the potential critical, important, urgent, lucrative, or undesirable nature of specific packets. Traffic management is a wide conceptual area of network processing that deals with how the underlying flow of real-time traffic, which can be composed of a continuous, massive, and time-varying collection of disparate and largely unrelated session packets from a staggering multi- tude of applications, must be treated in order to implement, monitor, and enforce specific QoS require- ments of the network. TRAFFIC MANAGERS AS STANDALONE CHIPS As we have seen in the first 10 chapters of the book, most powerful network processors already con- tain certain embedded capabilities that enable them to perform in some cases adequate and in other cases rudimentary traffic management operations on the traffic stream that they monitor and process. However, in order to perform high-speed, fine-granularity traffic management on information streams, highly specialized standalone chips called traffic managers are required. Traffic managers have sev- eral advantages: Traffic managers are off-the-shelf commercially available components. This means their cost is tremendously lower than if a designer designs a traffic manager from scratch. On many occasions, in principle, traffic managers can be mixed and matched with network processors or switch fabrics from different vendors. The best of each breed can be chosen to suit the design requir