Computing – Communications and Networks

We are now going to delve a bit more deeply into the components of a
computer network. We begin at the edge of network and look at the
components with which we are most familiar--the computers (for example,
PCs and workstations) that we use on a daily basis. Then, moving from the
network edge to the network core we have switchs and routers. Finally, we
have the access network – the physical link(s) that connect an end system to its
edge router – that is, to the first router on a path from the end system to any
other end system.

In computer networking jargon, the computers that we use on a daily basis are
often referred to as hosts or end systems. They are referred to as hosts because
they host (run) application-level programs such as a Web browser or server
program, or an e-mail program. They are also referred to as end systems
because they sit at the edge of the network.
Hosts are sometimes further divided into two categories: clients and servers.
Informally, clients often tend to be desktop PCs or workstations, whereas
servers are more powerful machines. But there is a more precise meaning of a
client and a server in computer networking. In the so-called client/server
model, a client program running on one end system requests and receives
information from a server running on another end system. This client/server
model is undoubtedly the most prevalent structure for Internet applications.
The Web, e-mail, file transfer, remote login (for example, Telnet), newsgroups,
and many other popular applications adopt the client/server model.
The other model used in computer networks is referred to as peer-to-peer
model. In this model the two hosts takes the same role and run the same
programs. A typical example of peer-to-peer application is the
teleconferencing.