A network is two or more devices that can communicate with one another and share
resources.Anetwork allows computer users to share files; communicate via e-mail; browse
the Internet; share a printer, modem, or scanner; and access applications and files.
Networks can be divided into two major categories—LANs and WANs. A LAN (Local
Area Network) is a group of devices that can share resources in a single area such as a
room or a building.AWAN (Wide Area Network) is communication between LANs. The
Internet is an example of a WAN as are two networks located in two cities.
Networks are vital to businesses today. They can even be found in many homes. A
technician must have a basic understanding of the devices that make up networks (computers,
printers, modems, etc.) and then learn network devices. You cannot bypass
computer repair and go straight into networking.
TYPES OF LOCAL AREA NETWORKS
There are two basic types of LANs, a server-based network and a peer-to-peer network.
With a server-based network, computer users login to a main computer called a server
where they are authenticated (authorized to use the network). The server is a more
powerful computer than a normal workstation. The server contains information about who
is allowed to connect to the network, and to what network resources (files, printer, and
applications) the network user is allowed access. A peer-to-peer network does not have
a central server. Instead, each computer is its own server. The computer user sets up passwords
to allow others access to the resources.Auser uses the network to access the remote
files, printer, applications, and so forth, from their own workstation. Server-based networks
are more common in businesses, whereas peer-to-peer networks are more common in homes
and very small businesses. A server-based network can consist of 10 or more computers;
in contrast, a peer-to-peer network usually has fewer than 10 computers.
A server-based network is more secure than a peer-to-peer network. This is because
the server is normally located in a locked network room or wiring closet. Also, the network
users and what they are allowed to do (their network rights and permissions) are configured
and stored on the network server. Servers have a special operating system loaded on
them called a NOS (Network Operating System). Examples of network operating systems
are Novell’s NetWare, Microsoft’s NT Server, 2000 Server, and 2003 Server. A network
operating system has utilities that allow computer user management (who is allowed onto
the network), resource management (what network applications, files, printers, etc. a user
can use), and security management (what a user is allowed to do with a resource such as
read, write, read and write, etc.). One userid and password is all a remote user needs to
access many network resources located throughout the business organization. A network
user can sit down at any computer in the organization, logon to the server, and start working
with the network resources.
The network
has one server in the center, four workstations, and two laser printers labeled LP1
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and LP2. The server has a database of users, CSchmidt, RDevoid, and MElkins, and their
associated passwords. The server also has three applications loaded—Microsoft Excel,
Microsoft Project, and Microsoft Word. These applications and associated documents are
stored on the server. Whether or not the users can access these applications and documents
and what they can do within each document is also stored on the server. In the Permission
column of the table located in Network Figure #1 is either R for Read or R/W for Read
/Write. This is an indication of what the user can do in a particular application. For example,
user CSchmidt has read and write access to Excel, Project, and Word. User MElkins can
only read Excel and Word documents, but she can read and write Microsoft Project documents.
User CSchmidt can print to either of the laser printers, but user RDevoid prints
only to the LP1 laser printer.
Another benefit of server-based networks is that a user can sit down at any workstation,
login to the server with his or her userid and password, and have access to all of the
network resources. For example in Network Figure attached, computer user RDevoid can sit
down at any workstation and have access to her Excel and Word documents and print to
laser printer LP1.



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