Chapter 5. Local Area Networks and Networks of LANs

A local area network (LAN) is a small interconnection infrastructure that typically uses a shared transmission medium. Because of such factors as the volume of traffic, the level of security, and cost, the network structure in a local area network can be significantly different from that for a wide area network. This chapter focuses on the fundamentals of local area networks and describes the internetworking concept at the LAN level. major topics are as follows :

• Basic LAN topology

• LAN protocols

• MAC and IP addresses

• Classification of MAC protocols

• Contention -access MAC

• Round- robin -access MAC

• Network of LANs

First, we explore some simple topologies of local area networks and see how a LAN is formed . We then extend the discussion of protocols presented in Chapter 2 to LAN protocols, focusing on medium access control (MAC) and addressing. We explore two well-known methods of link-access methods : contention and round-robin .

Another important topic is internetworking . Some pointers toward internetworking LANs with repeaters and bridges are provided. The focus of this chapter is primarily on layer 2 of the protocol stack reference model.