INTRODUCTION

The global internet is powered by thousands of interconnected networks in countries around the world. In order for South Africans to connect to these networks, undersea fibre optic cables are needed. These networks are all connected, but if a person wants to get information from overseas the data traffic must be carried over a submarine (underwater) cable (or in rare cases, a satellite connection). Telecoms infrastructure from local providers connect a person’s device to a local network. This will change internet connectivity, bandwidth and the way we play online games. A few companies plan to build their own internet submarine cable between Africa and Europe to increase the internet connectivity.

In this chapter, you will learn more about computer networks (including the internet). This chapter focuses on the different types of networks as well as the advantages and disadvantages of networks. You will learn about the different components needed for these networks, the different sizes of local area networks (LANs) and wide area networks (WANs) and about network architectures. You will also learn more about communication over networks and how it changed our lives.

UNIT
5.1 Uses of networks

In this unit, we will briefly look at each network’s uses. You will also learn more about the advantages and disadvantages of networks.

WHAT IS A NETWORK?

A computer network refers to a group of two or more computing devices that are connected by a communication medium allowing the computers to communicate electronically. A computing device on a network is usually referred to as a node, being connected to one another, it allows nodes to exchange data with one another using a connection media between them. The links can be established either over cable media such as wires or via a wireless media such as Wi-Fi.
The following are reasons for using networks:

1. COMMUNICATION

Everything, from the world wide web to online banking to multiplayer computer games, depends on the ability of computers to communicate. However, it is not just computers that communicate with each other, computer and telecommunication networks also connect people. Whether this is through video calls on a smartphone, emails from your computer, instant messaging services or social networks, computer networks allow people from across the world to easily communicate with one another.

2. ACCESSING RESOURCES

Networks allow computers to share and access resources with other computing devices connected to it.

• Data and information: Networks allow computers to share data and information. This can most easily be seen on the internet, where websites like Wikipedia share information on millions of different topics, but is also true for smaller home and business networks.
• Printers and scanners: Hardware devices like printers and scanners are not used that frequently by any single computer. A network allows several people to be connected to one printer or scanner, thus making optimal use of these resources.
• Software: Networks also allow people and computers to share software. Online applications like Office 365 and Google docs are examples of applications installed on only a few servers and shared by people around the world.
• Labour and money: Resources are not just restricted to computer resources but can also extend to real world resources like people and money. By seeking advice on the internet, you can gain access to experts from all over the world who can help you to resolve an issue you may be experiencing. Banking sites, investment sites and crowdfunding sites like GoFundMe.com gives you access to information on how to access funding and fundraising opportunities.
• Other hardware resources: Equipment such as portable disk drives, portable DVD drives, and plotters can be shared amongst many users on a network.

3. CENTRALISATION OF DATA

Data can be stored on one server instead of several devices. For example, on a small home network, all the data can be centralised by using a server. By doing this, anyone with access to the network can work with the data stored on the central server without needing to connect several external hard drives or flash drives to a computer.

4. TRANSFER OF FILES

One way in which data and information can be shared on a network is by sharing files. By sharing files, you allow users connected to the same network (whether that is a local network or the internet) to gain access to specific files.
Files can be shared in several different ways. These include:

• using the operating system’s file sharing utility
• placing the files on a Network-attached Storage (NAS) device or file server
• uploading the files to a website
• sending an e-mail with the files as attachments
• using file sharing websites like Google Drive, One Drive and Dropbox.

Most of these services not only allow you to share files, but also give you the option to limit how these files are used. For example, you may want to share the files for a group project in such a way that all the group members can amend them. In contrast, you may not want group members to change the details of, for example, a shared birthday invitation, so the invitation can be shared using the View only option.

5. INCREASED PRODUCTIVITY

The use of networks allow most people to work and study more productively. This is achieved by allowing people to:

• collaborate more easily.
• share files, thereby preventing work from being duplicated.
• share resources and information.
• quickly find answers to their questions by centralising useful information.

For example, as a programmer you might not be able to solve a programming problem. By using the internet you can speak to experts live and they would be able to guide you in solving the problem you may be experiencing. You could also look at the files of similar applications that have been developed to see how their creators solved a problem. Or you could work through several free, online programming courses and permanently improve your productivity. The same is applicable for most fields of study and work.

6. LEISURE

Access to the internet provides access to an almost unlimited amount of entertainment. Examples include:

• games
• multimedia
• books

ADVANTAGES AND DISADVANTAGES OF NETWORKS

The table below compares some of the advantages and disadvantages of connecting to a network.

Table 5.1: Comparison of the advantages and disadvantages of connecting to a network

5.1.1Choose a term/concept from COLUMN B that matches a description in COLUMN A. Write only the letter next to the question number (e.g. 1– A). There can be more than one answer to a question.

5.1.2Think about how you use networks. Write one paragraph about the biggest advantage and the biggest disadvantage of networks for you.

5.1.3You are working on a school project with two of your classmates; you need to determine how technology affected people’s lives. This project includes a number of research activities, interviews with people, sharing this information with each other and writing a report on your findings, recommendations and conclusion. As you do not live close to each other, you decided to use a network to communicate with each other about the project when needed.

Unfortunately, you do not yet have a network, and you must explain to your father why it is important to install a network.

a.In your discussion, give at least FIVE reasons why having a network installed will make your life easier or better.

b.Give at least ONE counter argument to each of the following disadvantages he gives back to you:

i.It can be addictive and waste large amounts of time.

ii.It can expose you to online crimes like identity theft and frauds.

iii.It can expose you to cyberbullying and abuse.

After the discussion, your dad saw your point and installed a network at home.

c.In order to complete your project, which tasks will you be able use a network for?

d.Describe an example of how you and your two class mates could collaborate on the project using the network in order to produce a better end product.

5.1.4Your school is hosting a large athletics event with four different schools participating. There is a large outdoor screen that will provide updated results and other announcements. Describe how using a network will be beneficial for each of the following:

a.Inputting the athlete’s position and performance as they come in from the various events.

b.Being able to display results in real time on the big screen.

c.Proving results that can be used to update the social media platforms of the four schools.

UNIT
5.2 Components of a network

To create any type of network you will need networking equipment. The networking equipment needed will, however, depend on the type of network you wish to establish. This unit will look at the different components needed to create wired and wireless networks.

Basic network components include the following:

• Nodes: This refers to a device connected to a network which is able to send and receive data. Examples of nodes include:

• printers
• servers
• workstations (PC’s or laptops)
• access points.

A network connecting three computers and one printer, along with two more wireless devices, has a total of six nodes.

• Network Interface Controller (NIC): Examples of NICs include:

• a wired NIC
• a wireless NIC.

• Communication media (wired and wireless): This refers to the physical channel through which data is sent and received.
• Network Operating System (NOS): A specialised operating system that allows additional security and settings.

OVERVIEW OF DIFFERENT COMMUNICATION MEDIA

WIRED NETWORK

A wired network is a network that uses a physical media to transfer data between two or more nodes. The transmission media for wired networks are:

• Unshielded Twisted Pair (UTP) and
• Fibre optic cables.

WIRELESS NETWORKS

A wireless network is a network that uses non-physical components to transfer data between two or more nodes. Local area networks are often wireless LANs (WLANs). Transmission media include :

• radio waves (wireless network)
• infrared signals (wireless network).

COMPARING COMMUNICATIONS MEDIA

UNIT
5.3 Types of networks

In this unit we will look at the different types of networks namely, personal, home, local and wide area network.

PERSONAL AREA NETWORK (PAN)

A personal area network (or PAN) covers a very small area. This type of network connects devices within a certain range and if you move outside of that range, the connection can be lost. For example, connecting your smartphone to a wireless speaker, headphones, or other wireless device.

HOME AREA NETWORK (HAN)

A home area network (or HAN) is a computer network that covers a larger area like your home. For example, connecting to a printer from anywhere in your house.

LOCAL AREA NETWORK (LAN)

A local area network (or LAN) covers a larger area like an office or a bigger premises. These computers can be connected to the network using either a wired or wireless connection media. Once connected, the computers on the network can share resources, information, transfer files and communicate with each other via email or web-based instant messaging channels.

The network LANs usually have a limited number of computers connected to them (between 2 and 25). However, there is no absolute limit. Because companies and homes usually create LANs for their personal use, the networks are configured to prevent outsiders from connecting to the network using security settings that require configuration for the network.

LANs have different uses, including transferring files and sharing network resources (like software and hardware). They are also used to play computer games competitively (called a LAN party), since the fast network allows the players on the network to play games without experiencing delays in the game (or lag time).

WIDE AREA NETWORK (WAN)

A wide area network covers a very large area – that could include all the people in a suburb, city or country. It is often used to refer to the internet, the world’s largest WAN.

Unlike a local area network, WANs are not private but are instead organised by communities or businesses. In order to join a WAN (like the internet) you need to seek permission from a company that manages the service. For example, to connect to the internet, you need to subscribe and pay a mobile network provider (MNP) like Vodacom or Cell C; or an internet service provider (ISP) like MWeb or WebAfrica, a monthly fee.

In the previous section we discussed a WAN and we learned that the internet is an example of a WAN. Let’s take a closer look at this.

THE INTERNET AS AN EXAMPLE OF A WIDE AREA NETWORK (WAN)

LOGGING ON TO A NETWORK

There are several reasons why we would want to log into a network or connect to a server. These allow you to share:

• files and data
• expensive devices
• backups and network security.

Anyone connecting to this network will have access to your resources (such as an internet connection and printer). In order to prevent unauthorised people from connecting to your network, you need to control who can and cannot access your network. To do this, you need something called access control. Access control is a security concept by which you increase the security of a network by tightly controlling the resources people have access to.

There are several different ways to implement access control, from requesting people to plug a network cable into a router to access the network (a form of physical access control) to using a log-on system that allows users to have a username and password to login to your network.

In South Africa, most internet connections make use of some form of access control. On mobile phones, this access control is linked to a SIM card, with limits set on the amount of data access you can use based on the account linked to your SIM card. When connecting to the internet through a wired connection (like DSL or fibre optic), your ISP may require you to enter a username and password which allows you to connect to their servers. Without an authenticated SIM card or a username and password, you cannot gain access to the internet.

Rather than simply allowing or blocking people from connecting to a network, access control gives you very specific control to manage how people can use the resources on your network. For example, on the internet, you may only have a limited amount of data available before your access is blocked. On a home network, the network can be set up in such a way that only certain users can add or remove files from the network. Thus, by thinking carefully about the limitations you would like to implement, you can create a network that is both secure and convenient to use.

CLIENT-SERVER AND PEER-TO-PEER NETWORKS

A network architecture refers to the differences in the way that the network is built. The two types of network architectures are peer-to-peer and client-server networks.

CLIENT-SERVER NETWORKS

A server is used to manage a client-server network, where computers (nodes) connect to the server. It ensures that authorised users have access to certain resources when logging on to a network. In a school, one would have the following:

• Many nodes, your PCs, connected via cables to the server.

PEER-TO-PEER NETWORKS

In a peer-to-peer network, each computer (node) on the network connects directly to the network AND to the other nodes. However, each computer has its own security. This means that the computer’s settings determine who is authorised to access the resources. Peers on this network are visible to each other and can share files and resources with each other.

In a peer-to-peer network, data flows between peers and most home networks are organised as peer-to-peer networks. This means that if your computer connects to your home network, it will have the same role and permissions as your mother’s notebook and your father’s smartphone. None of these devices organise the network nor do they need to be connected for the network to work correctly. Instead, each computer can connect and disconnect from the network automatically.

1.Describe the concept of a network.

2.List the reasons for using networks in order of importance. Explain your answer.

3.Evaluate the use of networks. Are they really beneficial? Support your answers.

4.For each type of network based on the communication medium used:

a.Illustrate and label the network connections and components.

b.Define each type of network, in your own words.

5.Complete the table comparing the communication medium in terms of accessibility, coverage and security.

6.Differentiate between client-server and peer-to-peer networks.

7.Explain the reasons for logging into a network and connecting to a server.

8.The IT class has invited interested parties and companies to exhibit business, career and study opportunities in IT and new developments in technology at their school. The exhibition will take place in the school hall over a weekend. A peer-to-peer LAN, which may be used by the exhibitors, will be provided in the school hall. The school has a separate client-server network that is in daily use. The LAN in the hall will be connected to the school’s router to provide internet access.

a.One advantage of using a network is that one can share hardware, such as printers.

i.State TWO other advantages of networking computer networks.

ii.Explain why a client-server network is more suitable than a peer-to-peer network to host a school’s administration system.

iii.What risks are there for the exhibitors linking their devices to the peer-to-peer network? Name and describe two.

b.The school uses UTP cables as a communication medium in their LAN.

i.What limitations are there to using UTP cables?

ii.Fibre-optic cables were installed in the area around the school as part of a WAN that the school would be able to use.

What medium is used to transfer data in fibre-optic cables?

iii.Motivate why fibre-optic cables would be advisable to use in a WAN.

c.The exhibitors can use laptop computers to connect to the internet, using the school’s wireless connection.

i.What hardware will a laptop computer require to connect wirelessly to the Internet?

ii.What are the advantages and disadvantages of wireless communication compared to wired communication.