Section 5.8. Summary

5.8. Summary

A local area network is a communication network that interconnects a variety of data communications devices to serve within a small community. The primary feature of a LAN is its ability to share data and software to provide common services, such as file serving, print serving, support for electronic mail, and process control and monitoring in office and industrial environments. We explored the three basic topologies of LANsbus, ring, and starusing fundamental knowledge on devices (Chapter 3) and on links (Chapter 4). The simplicity of bus LANs is an advantage when a cable can connect users through its taps. The star topology is a variation on the bus topology, whereby a hub provides connection capability. Star topology has the advantage of easier installation than bus topology.

For a user to place data onto a local area network, the network must be equipped with a MAC protocol to find ways of sharing its medium. The Address Resolution Protocol (ARP) is designed to convert a IP address to a MAC address or vice versa. Two well-known MAC methods are contention access , such as CSMA/CD for bus and star topologies, and round- robin access , such as token passing or token ring. CSMA/CD operates on a first-come first- served basis and clearly is one of the most popular access protocols. However, its frame collision during high-usage periods is indeed a bottleneck. Round-robin access is more appropriate than CSMA, as the round-robin method can regulate traffic under heavy loads.

We also covered important topics of internetworking and the use of repeaters, hubs, and bridges with switched LANs. A bridge operates at layer 2 and typically separates users into two collision domains. Routers, known as layer 3 switches, are also used to connect multiple subnets in larger LANs. Routers are typically designed to handle heavy traffic loads.

In Chapter 6, we explore wireless networks. We consider them from two angles: cellular structures and local area networks.