Chapter 2: Fundamental Concepts

Chapter 2: Fundamental Concepts

Overview

In this section we describe the fundamental concepts of label switching. Although there are differences among various approaches to label switching, certain concepts are common to all of these approaches?such concepts form the fundamental building blocks of label switching. A solid grasp of these concepts will help you understand the individual approaches to label switching as well as to compare them.

We begin this chapter with a description of the functional decomposition of network layer routing into control and forwarding components. We then proceed to describe label switching forwarding and control components. While describing the label switching control component, we present and compare various design alternatives. We then describe the type of devices that are needed to support label switching, followed by a brief discussion of the relationship between label switching and network layer routing and addressing. The chapter concludes with a brief summary.

2.1 Network Layer Routing Functional Components: Control and Forwarding

Network layer routing can be partitioned into two basic components: control and forwarding. The forwarding component is responsible for the actual forwarding of packets from input to output across a switch or router. To forward a packet the forwarding component uses two sources of information: a forwarding table maintained by a router and the information carried in the packet itself. The control component is responsible for construction and maintenance of the forwarding table.

Each router in a network implements both control and forwarding components. The actual network layer routing is realized...

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Switching in IP Networks: IP Switching, Tag Switching, & Related Technologies

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Chapter 2: Fundamental Concepts

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