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1.1. History
The
idea of networking is probably as old as telecommunications itself.
Consider people living in the Stone Age, when drums may have been
used to transmit messages between individuals. Suppose caveman A
wants to invite caveman B over for a game of hurling rocks at each
other, but they live too far apart for B to hear A banging his drum.
What are A's options? He could 1) walk over to
B's place, 2) get a bigger drum, or 3) ask C, who
lives halfway between them, to forward the message. The last option
is called networking.Of course, we have come a long way from the primitive pursuits and
devices of our forebears. Nowadays, we have computers talk to each
other over vast assemblages of wires, fiber optics, microwaves, and
the like, to make an appointment for Saturday's
soccer match.[1] In
the following description, we will deal with the means and ways by
which this is accomplished, but leave out the wires, as well as the
soccer part.[1] The original spirit of which (see
above) still shows on some occasions in Europe.
We
define a network as a collection of hosts that
are able to communicate with each other, often by relying on the
services of a number of dedicated hosts that relay data between the
participants. Hosts are often computers, but need not be; one can
also think of X terminals or intelligent printers as hosts. A
collection of hosts is also called a site.Communication
is impossible without some sort of language or code. In computer
networks, these languages are collectively referred to as
protocols. However, you
shouldn't think of written protocols here, but
rather of the highly formalized code of behavior observed when heads
of state meet, for instance. In a very similar fashion, the protocols
used in computer networks are nothing but very strict rules for the
exchange of messages between two or more hosts.
