Hardware Reference
In-Depth Information
businesses, but not with the general public, are called extranets. As with intranets, the same
web browsers and other software are used to access the content.
Note
Both intranets and extranets rely on firewalls and other security tools and procedures to keep
their private contents private.
Requirements for a Network
Unless the computers that are connected know they are connected and agree on a common means of
communication and what resources are to be shared, they can't work together. Networking software is
just as important as networking hardware because it establishes the logical connections that make the
physical connections work.
At a minimum, each network requires the following:
• Physical (cable) or wireless (usually via radio frequency [RF]) connections between
computers.
• A common set of communications rules, known as a
network protocol
.
• Software that enables resources to be served to or shared with other network-enabled devices
and that controls access to the shared resources. This can be in the form of a network operating
system or NOS (such as older versions of Novell NetWare) that runs on top of an operating
system; however, current operating systems (OSs) such as Windows, Mac OS X, and Linux also
provide network sharing services, thus eliminating the need for a specialized NOS. A machine
sharing resources is usually called a
server
.
• Resources that can be shared, such as printers, drives, modems, media players, and so on.
• Software that enables computers to access other computers sharing resources (servers).
Systems accessing shared resources are usually called
network clients
. Client software can be
in the form of a program or service that runs on top of an OS. Current OSs such as Windows,
Mac OS X, and Linux include client software.
These rules apply both to the simplest and the most powerful networks, and all the ones in between,
regardless of their nature. The details of the hardware and software you need are discussed more
fully later in this chapter.
Client/Server Versus Peer Networks
Although every device on a LAN is connected to every other device, they do not necessarily
communicate with each other. There are two basic types of LANs, based on the communication
patterns between the machines: client/server networks and peer-to-peer networks.
Client/Server Networks
On a
client/server
network, every computer has a distinct role: that of either a client or a server. A
server
is designed to share its resources among the client computers on the network. Typically,
servers are located in secured areas, such as locked closets or data centers (server rooms), because
they hold an organization's most valuable data and do not have to be accessed by operators on a
continuous basis. The rest of the computers on the network function as
clients
(see
Figure 17.1
).
