Network Traffic Management

Network resources are shared as needed by a community of users. Without effective traffic controls, networks are vulnerable to possible congestion when the offered traffic exceeds the network capacity, leading to serious deterioration of network performance. This chapter gives an overview of traffic control methods and their underlying principles. The main preventive controls are admission control and access regulation (policing). They seek to avoid congestion by limiting the amount of traffic entering the network. Within the network, packets may have different requirements for reliable or timely delivery. These requirements are recognized by packet scheduling and buffer management algorithms implemented in switches and routers. At the transport layer, protocols such as TCP can adapt their traffic rate to the level of congestion. Finally, this chapter covers the question of measurement and verification of network performance. INTRODUCTION Although an analogy between computer networks and automobile highways is simplistic, the view of networks as a type of infrastructure points out the need for traffic control. Highways have a limited capacity which can be exceeded when many people want to travel at the same time. Vehicles begin to slow down and back up in a congested area. The backup spreads if traffic approaches the congested area faster than traffic can leave. Similarly, computer networks are designed to handle a certain amount of traffic with an acceptable level of network performance. Network performance will deteriorate if the offered traffic exceeds the given network capacity.