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Basic Computer NetworkingBriefing Paper—Part 2 of 5Network Types and Equipment

1

1Connectingcomputers

3Email

networking

5Network server

hardware

4Global andprivate IP

addresses

2 Network typesand equipment

Contents

What is a simple network? .................................. 1 What is a LAN?.................................................. 1 What is a WAN?................................................. 1 Types of LAN .................................................... 1 What devices form a network? ............................ 2 Hubs................................................................ 2 Routers ............................................................ 2 Servers ............................................................ 2 What’s a peer-to-peer network? .......................... 3 What’s a client-server network? .......................... 3 Glossary........................................................... 3 What is a simple network?

As described in Part 1 of this series, a simple network is

formed when two or more computers are connected to

each other. The digital information in the first PC istranslated via a Network Interface Card (NIC) into a

network language. The information then travels via the

connection (such as cable or wireless). The NIC of thesecond PC receives the data and translates the

information into a digital language that the receiving PCcan understand.

Networks are usually designed for many users, so they

consist of many computers and different computerdevices. An important feature of a computer network is its

physical configuration. In this paper we look at how

networks are arranged.

What is a LAN?

A Local Area Network (LAN) is a system of communication

between two or more computers, covering a local area.For example, a LAN could be set up in a home, office or

small group of buildings, such as a college.

What is a WAN?

A Wide Area Network (WAN) spans a relatively large

geographical area. A WAN consists of two or more LANs

which are often connected by public networks. They canalso be connected by leased line or satellite.

Wide Area Network (WAN)

What’s different about LANs, WANs and the internet?

LANs and WANs are closed networks, for authorised users.WANs allow users to safely exchange data with computers

in remote locations in the same way as a LAN.

Unlike the controlled access of the LAN and WAN, the

internet is an open network, where everyone and anyone

can participate.

Types of LAN

A LAN is made up of cables and nodes. Nodes are thedevices connected in the network (such as a computer or

a printer). There are three common types of LAN: star,

bus and ring.

Three types of Local Area Network (LAN)

Bus: Nodes are

connected by branchesto a backbone.

Ring: Nodes are connected

in a ring configuration. Alsoknown as Token Ring.

Star: Nodes are

connected in aradial pattern with a

central connectionpoint.



2

What devices form a network?

Networks deploy many different hardware components,

known as devices. They are connected as resources for

network users. You are already familiar with PCs, printersand other office equipment. Other equipment that you

may not be familiar with are hubs, routers and servers.

These devices perform core network functions.

Common network devices or nodes

Hubs

Hubs are junction devices. They provide convenient

connection points for several cables on a network. Thereare two types of hub—repeater and switching.

Repeater hub Switching hub

A repeater hub is a simple connection point used in star

topology LANs (refer to the "Star" diagram on page 1).Data from one node is distributed to all nodes connected

to the hub, in a straight line transfer. It is suitable for

small networks.

Repeater hubs cannot transmit and receive data at the

same time. They attempt to prevent signal collisions byusing a method known as Carrier Sense Multiple Access

with Collision Detection (CSMA/CD). With CSMA/CD, a

node checks that there is a break in the traffic beforesending a signal. However, even with CSMA/CD, when

multiple nodes try to send signals, collisions may occur.

A switching hub is more efficient when the network

traffic increases. Data from one node is distributed only tothe destination node, not to all nodes.

Switching hubs overcome the problem of data collisions,with an internal structure like a highway interchange.

They also take advantage of the features of Unshielded

Twisted Pair (UTP) cable. Multiple nodes can send andreceive signals simultaneously, without collision.

The improved service offered by switching hubs and their

decreasing price tag, means they are now used widely inall types of networks. It is common for many repeaterhubs to be linked by a switching hub, to create a network

domain.

Routers

A router is a network device to connect different network

domains, for example LAN to LAN. Like the switching hub,

it determines the route for sending data via the network tothe target location. In addition, it can send data to an

external network. A router may be connected to switching

hubs, but not to repeater hubs.

The picture below shows the two types of hubs and a

router in a typical network domain.

Hubs and routers in a typical network domain

Servers

The network server is a special or dual-use computer that

provides network services to the other computers on the

network. For example, a mail server provides emailreception and distribution services, while a printer server

provides printing device services to clients. The software

installed on the server indicates the type of services it

offers.

The relationships between devices and servers in a

network is an important way to distinguish the two main

network types—peer-to-peer and client-server networks.

What is a domain?

The word 'domain' is used in several ways:

1. In general, a domain is an area of knowledgeidentified by a name. Typically, the

knowledge is a collection of facts about

program entities or network points or

addresses.

2. In Windows NT and Windows 2000, a domainis a set of network resources (for example,

applications and printers) for a group of

users. The user logs in to the domain toaccess the resources, which may be located

on several different servers in the network.

3. In a network, a collision domain refers to asmall group of computers, connected by a

repeater hub. The computers all use the same

method of CSMA/CD to correct data collisions

on the domain.

4. On the internet, a domain is a set of networkaddresses, organised in levels. The top level

identifies location or purpose (for example,.au or .com). The second level identifies the

internet (IP) address.



Prepared by Ricoh Asia Pacific for

Version 0.003, October 2005

3

Comments?

Please send any feedback about this document to:

[email protected] [email protected]

What is a peer-to-peer network?

A peer-to-peer network is where computers are all

connected to the network in the same way. Each

computer can act as a client or a server to any user onthe network.

All PCs can share resources such as printers

The software settings on each computer are very simple

to manage, but if a computer is not turned on, it isimpossible to use the resources provided by that

computer. Also, when someone is accessing the resourcesof another computer, the perfomance of the computer

providing the resource declines.

A peer-to-peer network is generally used for small-scale

LANS with five to ten devices. For bigger networks, theclient-server network is used.

What is a client-server network?

A client-server network consists of at least one networkserver connected to other network devices, which act as

clients.

Client-server network

There are many advantages of a client-server network,compared with a peer-to-peer network. By installing a

server that specialises in storage and transfer of data, forexample, it is no longer necessary to rely on individual

computers to share resources. This also eliminates the

decline in performance caused by one computer accessingthe resources of another computer.

Nevertheless, if you choose a client-server network youmust be prepared to employ a specialist to maintain the

server and administer the network. The cost usually

means that it is used in medium to large-scale LANs. Morerecently, single-function low-priced servers have reached

the market and are starting to be used in smaller and

medium-sized networks.

Glossary

Client

A computer that can request information or processing

from a server. Clients and servers can be connected to

each other on a LAN, a WAN or via a remote connection.

IP address

Internet Protocol address.

Also known as ‘internet address’. A unique number for a

computer or device, such as a printer, connected to the

internet, identifying its location. Usually written as fournumbers or sequences of numbers separated by periods—

for example, 114.151.8.3.

LAN

Local Area Network.

A group of computers and associated devices—such as

printers—that share a common communications line, and

usually share the resources of a single server within a

small geographic area—for example, an office building.

NIC

Network Interface Card.

A board inserted inside a computer or peripheral device so

that it can be connected to a network. Also called a

Network Interface Board (NIB).

Node

A generic word for any entity that can access a network.

Also known as a device.

Server

A computer on a LAN that manages network resources.

Servers are usually dedicated, meaning they do not

perform any other tasks besides their server tasks.

Token Ring

Computers are connected in the shape of a closed ring, so

that each device is connected directly to two other devices,one on either side of it. Only one computer may send data

at any one time, which prevents data collision on the

network. If one computer continued sending data, it wouldoccupy the LAN to the exclusion of all others. To prevent

this problem, data is limited to a length of a few kilobytes.

These small units of data are referred to as ‘packets’ or

‘frames’.

Ring topologies are relatively expensive and difficult toinstall, but they offer high bandwidth and can span large

distances.

WAN

Wide Area Network.

A group of computers and associated devices—such as

printers—that share a common communications line,

extending over distances greater than one kilometre.A WAN usually consists of two or more LANs. Devices are

connected to a WAN by public networks, such as the Public

Switched Telephone Network (PSTN), or by leased line, or

satellite.

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