is a set of protocols developed to allow cooperating computers to share resources
across a network. It was developed by a community of researchers centered around
the ARPAnet. Certainly the ARPAnet is the best-known TCP/IP network. However as
of June, 87, at least 130 different vendors had products that support TCP/IP,
and thousands of networks of all kinds use it.
most accurate name for the set of protocols we are describing is the "Internet
protocol suite". TCP and IP are two of the protocols in this suite. (They
will be described below.) Because TCP and IP are the best known of the protocols,
it has become common to use the term TCP/IP or IP/TCP to refer to the whole family.
It is probably not worth fighting this habit. However this can lead to some oddities.
For example, I find myself talking about NFS as being based on TCP/IP, even though
it doesn't use TCP at all. (It does use IP. But it uses an alternative protocol,
UDP, instead of TCP. All of this alphabet soup will be unscrambled in the following
The Internet is a collection of networks, including the Arpanet, NSFnet,
regional networks such as NYsernet, local networks at a number of University and
research institutions, and a number of military networks. The term "Internet" applies to this entire set of networks.
is a layered set of protocols. In order to understand what this means, it is useful
to look at an example. A typical situation is sending mail. First, there is a
protocol for mail. This defines a set of commands which one machine sends to another,
e.g. commands to specify who the sender of the message is, who it is being sent
to, and then the text of the message. However this protocol assumes that there
is a way to communicate reliably between the two computers.