A local-area network (LAN) is a communications system designed to transmit and receive digital
information between computers. A LAN consists of nodes that are interconnected by links. Nodes
are the hardware connected to the network, such as personal or microcomputers, printers, large
capacity hard drives, and so on. Links are the communications media, such as twisted-pair wire,
coaxial, or fiber-optic cables that connect the nodes. In most applications, the LAN interconnects
a relatively small number of personal computers (PCs), data storage devices, printers, and other
peripherals. These nodes and links usually cover a relatively small geographical area, such as an
office or a department. Through common usage, the term local-area network can also refer to much
larger systems, such as the SNAP III system on a ship, which could have literally hundreds of
terminals and miles of cables. For our purposes, we will be using a small system in our discussion
Any device connected to the network can send and receive data on the network. A majority of
data exchanged over a network is text and graphics, which is assembled as structured data that can
be manipulated by computers. Unstructured data, such as pictures and facsimile messages, can be
stored and retrieved efficiently, but cannot be manipulated easily by the computer.
After completing this chapter, you should be able to:
Describe the major components of a LAN.
State the types of cable used in a LAN.
State the function of the network interface card.
Describe the function of the various network servers required by a LAN.
Describe the function of the central mass storage area of a LAN.
Describe the Open System Interconnection (OSI) Reference Model used in the design
and implementation of a LAN.
Describe the advantages and disadvantages of the different LAN topologies.
Describe the hardware systems used in LANs.
Describe the function of the software operating system of a LAN.