INTRODUCTION TO NETWORKING
Upon successful completion of this chapter you will be able to:
1.
Define the three categories of networks
2.
Understand the difference between peer-to-peer and server-based networks
3.
understand network topology and services
4.
Set up a simple peer to peer network using a non-configurable protocol
SUMMARY OF NEW TERMS
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LAN—local area network
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MAN—metropolitan area network WAN—wide area network
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Peer-to-peer Network—a network of computers where each computer is responsible for its own
logon authentication and security
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Server-based Network—a network of computers where one or more assigned computers are
responsible for the logon authentication and security of all member computers
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Network Topology—the physical layout of the network wiring and data transmission characteristics
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Network Services—features provided by a network
TYPES OF NETWORKS
A network consists of two or more computers that can communicate with each other, share resources (such as
hard disks, printers and CD-ROMs), and access remote hosts or other networks to exchange files, data, and
information or allow electronic communications.
Networks can be broken up into three main areas—local area network (LAN); metropolitan area network
(MAN); and wide area network (WAN).
A LOCAL AREA NETWORK (LAN)
A local area network (LAN) refers to a combination of computer hardware, software and transmission media
that is relatively small. LANs normally do not exceed tens of kilometers in size and tend to use only one type of
transmission medium. It is generally limited to a geographic area such as a school, a building or a campus.
In a typical LAN configuration, one computer is designated as the file server. It stores all of the software that
controls the network, as well as the software that can be shared by the computers attached to the network.
Computers connected to the file server are called workstations. The workstations can be less powerful than
the file server, and they may have additional software on their hard drives.
Generally, there are two types of LAN—peer-to-peer and server based. A server-based network is sometimes
called a 'client/server' network.
A METROPOLITAN AREA NETWORK (MAN)
A metropolitan area network (MAN) is a network that is larger than a LAN. It is called metropolitan since it
covers larger geographic areas of a city (a few tens to about 100 kilometers) such as cities or council districts.
Different hardware and transmission media are often used in MANs because they must efficiently cover these
distances or because they don't require complete access to locations between the networked sites. By
interconnecting smaller networks within a large geographic area, information is easily sent throughout the
network. Local libraries and government agencies often use a MAN to connect to citizens and private
industries.
A WIDE AREA NETWORK (WAN)
A wide area network (WAN) includes all networks larger than a MAN. WANs connect larger geographic areas
such as states, or different countries. Dedicated trans-oceanic cabling or satellite uplinks may be used to
connect this type of network.
A WAN is complicated. It interconnects LANs (which may be at opposite sides of a country or located around
the world) and MANs to global communications networks like the Internet. To users, however, a WAN will not
appear to be much different than a LAN or a MAN.
PEER-TO-PEER NETWORKS
Peer-to-peer networks are a very simple example of local area networks and allow every node to both request
and provide network services. Peer-to-peer network software is designed so that peers perform the same or
similar functions for each other. Examples of peer-to-peer network operating systems include:
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Microsoft Windows for Workgroups 3.11®, M Microsoft Windows 95/98, ME
Microsoft Windows NTC) Workstation a Novell NetWare® Lite
Microsoft Windows XP® Professional
Peer-to-peer networks are also known as workgroups and are typically used where there are 10 or fewer users
on the network. There is no responsible administrator—each user acts as the administrator for their own
workstation and chooses what resources and data they share on the network and who can access them.
Advantages of a peer-to-peer network are:
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Simple to install
Relatively cheap
Disadvantages of a peer-to-peer network are:
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Administrative chaos—administration becomes messy with multiple user accounts and
'passwords for a single user who accesses different workstations
Security can be compromised with users generally sharing passwords to the same resource.
No centralized backups of data
SERVER-BASED NETWORKS
Server-based networks involve strictly defined roles. By definition, a server-based network places restrictions
on which entity may make requests and which entity can service those requests. Computers known as file
servers facilitate the processing of data and communication between other computers on the network. These
other computers are called workstations. Currently the most popular personal computer network operating
systems include:
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Novell NetWare
Windows NT Server
Windows 2000 Server® and Advanced Server®
Windows Server 2003
UNIX (including various distributions of Linux)
Server-based networks are usually recommended for networks with 10 or more users and perform specialised
tasks such as:
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File and print servers—manage user access to files and printers
Application servers—maintain roles of the server in a client/server environment, such as
databases and web servers
Mail servers—operate like an application server in that there are separate server and client
applications, with data selectively downloaded from the server to the client
Server-based networks are generally harder to install, configure and manage than a peer-to-peer network, but
provide better security to user's files and network resources. Backing up of data is easier to manage and can be
scheduled to occur automatically.
NETWORK TOPOLOGY
OVERVIEW OF LAN WIRING TOPOLOGY
Each LAN standard has its own rules for LAN wiring. These rules define the connecting media, the hardware
requirements, and the way the various components are arranged. There are three factors that determine the
nature of a local area network (LAN):
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Topology
Transmission media
Medium access technique
TOPOLOGY
The geometrical arrangement or physical layout of the network-wiring scheme is called the topology.
T HERE ARE TWO TYPES OF TOPOLOGIES :
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Physical topology
Logical topology
The physical topology of a network describes the way in which the actual cables are routed. It does not specify
the types of devices, connectivity methods or addresses on the network. The logical topology describes the
way that the network behaves while passing information between various devices
PHYSICAL TOPOLOGY
The complete physical structure of the transmission media is called the physical topology.
The physical topology of a network is generally classified as one of three basic geometric shapes—bus, ring or
star. These three shapes can be combined to form hybrid topologies, such as star-wired ring, star-wired bus
and daisy chains.
When choosing a physical network topology, special attention should also be paid to the following
characteristics:
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Relative ease of installation
Relative ease of reconfiguration
Relative ease of troubleshooting
Maximum number of units affected by a media failure
Cost, performance, reliability, future growth, type and length of cable
LOGICAL T OPOLOGY
The logical topology of the network defines its data transmission characteristics, such as the network transport
model. When dealing with local area networks, the two most common logical topologies are Ethernet and
token ring.
HOW NETWORKS ARE USED
Networks join two or more computers together to provide a rapid method for sharing and transferring data.
The many features provided by a network are generally referred to as services. The most common service on a
network is usually email, although printing, file sharing, Internet access, remote dial-in, mainframe
communication and management services are just as important to the overall functionality of the network.
Large corporate networks may have individual servers to accomplish each of these tasks, although smaller
networks will generally have only one or two servers providing all of the services.
Before networks were available, the only way to share information between .computers was to copy it to a
portable form of storage media, such as a floppy disk, and then physically carry that media from the first
computer to the second. This early method of data sharing became known as 'sneaker net', due to the fact that
most people wore 'sneakers' on their feet when they were moving the media from one computer to another.
FILE AND PRINT SERVICES
A network's file services can be used to share application software, such as word processors, databases and
spreadsheets or email programs. These programs can be run from a central server, which means they don't
have to be installed locally on every computer. This eliminates the need to spend time and energy installing
updates and tracking files on independent computers throughout the building, because everything is stored in
one central location.
File services also allow users the ability to share data and other resources quickly and inexpensively. Whereas
it may take days to send a letter to a person on the other side of the world, it now takes seconds by email.
Multimedia files can be quite difficult to transfer from one PC to another by floppy disk because of their large
file sizes, but are easily transferred across a network. Web sites can keep us up to date with the latest news
and information. Users are also able to take advantage of sharing things such as CD-ROMs, fax modems and
scanners, which may be in short supply.
Using the network's- print services allows us to share printers across the network, which reduces costs and
saves time. Instead of needing a local printer for each computer, the administrator can set up one or a few
printers for users to share. The number of printers would depend on the network's size. Although the network
printer may cost several thousand dollars to buy, the overall cost of providing printing to all users is reduced.
Administration and troubleshooting is also easier with fewer printers. In fact, administrators may be able to
diagnose and fix printer problems from their workstation, without having to physically visit the printer.
CENTRALISED SECURITY AND ADMINISTRATION
Files and programs on a network can be secured with permissions which only allow authorised users access.
Users may only need to logon once with an authorised user account and password, which will allow them to
access data and network resources. What one user can see on the network another user may not be able to
see. This doesn't mean it's not there but only that it is hidden from the user who hasn't been given access.
Networks allow users to access their data from anywhere on the network. This means if a student was working
on a file and saved this to the network they would not have to go back to the same computer to access the file.
*Backing up of data also becomes easier because the administrator would only need to backup one computer
(the server). All of the important data would be stored in one central location, giving tighter control and
security over the data. The administrator can ensure data is regularly backed up according to company or
institution policies. This will save much time, as they do not have to backup each individual workstation.
MAIL SERVICES
The transfer of electronic mail (email) between users on a local area network, or between users on the local
area network and the Internet, is managed by the network's mail services. Email enables personal and
professional communication for all personnel, e.g. between students on a school or university network, or
between students and teachers. If the teacher or lecturer has a private Internet email address, the student
may be able to use that address to communicate with the teacher outside of the local area network. Apart
from general email communications, mail services are used for other tasks such as intelligent email routing
(e.g. forwarding a message to a supervisor if an email goes unopened or unanswered by a particular user for
longer than a pre-set amount of time), notification, scheduling, management and gateways to other mail
servers.
COMMUNICATION SERVICES
The network's communications services allow external users to connect to the network remotely, usually
through a telephone line and modem. They also allow users on the network to connect to other machines or
networks outside of the local area network. Most network operating systems (NOS) have these services builtin. Windows NT 4.0 has a remote access server (RAS), Windows Server 2003 has a routing and remote access
server (RRAS) and Netware has a network access server (NAS). The computer running these services is known
as the communications server and is responsible for managing communications. Once a user has logged on and
been authenticated through the communications server, they have the same access privileges they would
enjoy if they were sitting at a workstation that was physically attached to the network (unless the
administrator has restricted access when logged on remotely).
INTERNET SERVICES
Internet services include World Wide Web servers and browsers; file transfer capabilities, Internet addressing
schemes and security filters. They are essential to modern day networks to enable global communication and
data exchange.
MANAGEMENT SERVICES
Small networks could be managed easily, but as networks have grown, these management tasks have become
much more complex, instead of being able to walk into the next room to diagnose or resolve a problem; a
network administrator may now be dealing with computers, separated by many kilometers. They may even be
located on different continents.
Management services allow network administrators to centrally administer large and complicated networks.
The tasks involved can include traffic monitoring and control, load balancing, hardware diagnosis and failure
alert, asset management, license control and monitoring, security auditing, software distribution, address
management, and backup and restoration of data.