Local Area Networks (LANS)
LANs were originally intended for the interconnection of mainframe computers with
peripherals. Now they encompass interconnection networks of personal computers
within a confined geographic area.
Most LANs used a shared medium. A protocol is required to access this medium.
This type of protocol is known as a Medium Access Control (MAC) protocol. There
are a number of protocols of this type, but generally can be classed as random access
or scheduled access. Ethernet is an example of a random access protocol, and Token
Ring an example of scheduled access.
Most of these protocols will only operate over short distances. If they are designed to
operate over tens of kilometres they may be applied to Metropolitan Area Networks
(MANs)
LANs may be interconnected to form larger networks via repeaters and bridges. The
LAN can be made to scale to accommodate hundreds of host computers or other
devices using bridged networks, however, they are not suitable for very large
numbers of hosts, or for large geographic areas.