Chapter 1. Desktop Technologies

This chapter covers the following key topics:

• Legacy Ethernet This section explains the operations and implementation rules of legacy 10 Mbps CSMA/CD systems.

• LAN Frames This section presents various common formats for transporting packets over Ethernet.

• Fast Ethernet A now popular desktop Ethernet migration, this uses 100 Mbps technology. This section describes its characteristics and some of the common media options.

• Gigabit Ethernet As the highest speed Ethernet available today, this technology finds immediate utility for trunking Catalysts and connecting high performance servers. This section describes media options and characteristics.

• Token Ring Token Ring, the other popular LAN alternative, operates very differently from Ethernet. This section provides a brief overview of Token Ring.

Since the inception of local-area networks (LANs) in the 1970s, numerous LAN technologies graced the planet at one point or another. Some technologies became legends: ArcNet and StarLAN, for example. Others became legacies: Ethernet, Token Ring, and FDDI. ArcNet was the basis for some of the earliest office networks in the 1980s, because Radio Shack sold it for its personal computer line, Model II. A simple coaxial-based network, it was easy to deploy by office administrators for a few workstations. StarLAN, one of the earliest twisted-pair network technologies, became the basis for the Institute of Electrical and Electronic Engineers (IEEE) 10BaseT network. Running at 1 Mbps, StarLAN demonstrated that networking over twisted pair was feasible. Both ArcNet and StarLAN enjoyed limited success in the market because higher speed technologies such as 10 Mbps Ethernet and 4 Mbps Token Ring were introduced soon afterwards. With the higher bandwidth capacity of newer network technologies and the rapid development of higher speed workstations demanding more network bandwidth, ArcNet (now fondly referred to as ArchaicNet) and StarLAN were doomed to limited market presence.

The legacy networks continue to find utility as distribution and backbone technologies for both manufacturing and office environments. But like ArcNet and StarLAN, even these technologies see higher speed networks such as Fast Ethernet, High Speed Token Ring, and ATM crowding into the network arena. However, the legacy systems will remain for many more years due to the existence of such a large installed base. Users will replace Ethernet and Token Ring in phases as applications demand more bandwidth.

This chapter discusses the legacy network technologies, Ethernet and Token Ring, as well as Fast Ethernet and Gigabit Ethernet. Although Gigabit Ethernet is not yet a popular desktop technology, it is discussed here because of its relationship to Ethernet and its use in Catalyst networks for trunking Catalysts together. This chapter also describes how the access methods operate, some of the physical characteristics of each, and various frame formats and address types.