Chapter 3. Underlying Technologies
We can think of the Internet as a series of backbone networks that are run by international, national, are regional ISPs. The backbones are joined together by connecting devices such as routers or switching stations. The end users are either part of the local ISP LAN or connected via point-to-point networks to the LANs. Conceptually, the Internet is a set of switched WANs (backbone). LANs, point-to-point WANs, and connecting or switching devices.
Although the TCP/IP Protocol Suite is normally shownas five-layer stack, it only defines the three upper layers: TCP/IP is only concerned with the network, transport, and application layers. This means that TCP/IP assumes the existence of these WANs, LANs, and the connecting devices that join them.
As a brief review, we touch upon some of these underlying technologies in this chapter.
OBJECTIVES
The chapter has several objectives:
- To briefly discuss the technology of domainant wired LANs, Ethernet, including traditional, fast, gigabit, and ten-gigabit Ethernet.
- To briefly discuss the technology of wireless WANs, including IEEE 802.11 LANs, and Bluthtooth.
- To briefly discuss the technology of point-to-point WANs including 56K modems, DSL, cable modem , T-lines, and SONET.
- To briefly discuss the technology of switched WANs including X.25, Frame Relay, and ATM.
- To discuss the need and use of connecting devices such as repeaters (hubs), bridges (two-layer switches), and routes (three-layer switches).
3.1 WIRED LOCAL AREA NETWORKS
A local area network (LAN) is a computer network that is designed for a limited geographic area such as a building or a campus. Although a LAN can be used as an isolated network to connect computers in an organization for the sole purpose of sharing resources, most LANs today are also linked to a wide area network (WAN) or the Internet.
The LAN market has seen several technologies such as Ethernet, token ring, token bus, FDDL, and ATM LAN. Some of these technologies survived for a while, but Ethernet is by far the dominant technology.
In this section, we first discuss the IEEE standard Project 802, designed to regulate the manufacturing and interconnectivity between different LANs. We then concentrate on the Ethnet on the Ethernet LANs.
Although Ethernet has gon through a four-generation evolution during the last few decdes, the main concept has remained the same. Ethernet has changed to meet the market needs and to make use of the new technologies.
IEEE Standards
In 1985, the Computer Society of the IEEE started a project, called Project 802, to set standards to enable intercommunication among equipment from a variety of manufacturers. Project 802 does not seek to replace any part of the OSI or the Internet model. Instead, it is a way of specifying functions of the physical layer and the data link layer of major LAN protocols.