9.1 Concepts used in networks
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Chapter 8: Extended software concepts
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Chapter 10: Types of networks: PAN/HAN
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CHAPTER OVERVIEW
At the end of this chapter, you should be able to:
- Explain the different concepts used in networks.
- Understand how networks are used.
- Discuss the advantages and disadvantages of networks.
- Identify the social implications that are associated with networks.
INTRODUCTION
A computer network consists of two or more computers and other hardware devices that are linked together through communication channels to share electronic communications and resources, such as printers with various users.
Something to know
The Semi-Automatic Ground Environment (SAGE) computer system was invented by two MIT professors during the 1950s and became operational in 1961. Because of America’s size, the speed of the military attack planes and the possibility of nuclear attacks by the Russians, the US military decided that they needed an air-defence system that would identify and intercept enemy planes before they could do any damage.
SAGE was, therefore developed, using techniques learned from World War II radar development. Weighing over 250 tonnes, SAGE was one of the largest computers ever built and consisted of 23 bunkers all over the US and one in Canada; each having a SAGE computer that could track 400 planes. As it consisted of a network of long-distance communications technology through landlines and ground-to-air radio links and interactive display terminals, it could differentiate between enemy and friendly planes by keeping track of flight plans. What made SAGE so extraordinary, is the fact that it was the first network-based computer system, laying the foundation for the entire internet age.
In this chapter, you will learn about networks, the different concepts used in networks, and the advantages and disadvantages of networks. You will also learn how to use networks in an ethical and correct way.
UNIT
9.1 Concepts used in networks
Looking at the definition of a computer network in the “Introduction”, you will remember that a computer network consists of two or more computers and hardware devices linked together through communication channels to share electronic communications and resources with various users.
In computer networks, computing devices are called nodes and share data with each other through data links. These links are sent over cable media such as wires, optic cables, or wireless media such as Wi-Fi. The connected computers also share resources, such as access to printers, with the most common resource being the internet.
There are two common types of networks:
1. Home Area Network (HAN): A HAN is a very small network that usually covers a single home or home office.
2. Personal Area Network (PAN): A PAN is similar to a HAN, but even smaller! It refers to a network that is built for a single person and contains all the devices connected to this network.
Most organisations, such as schools and businesses, have computers that are connected to a central computer called the network server. This server is the main computer that manages the communication between all the other computers on the network. A network client refers to the hardware or software that can access services made available by a server.
Network administrators are the people that are part of a technical support team, and who can modify and change the network according to the organisation’s needs. The administrator can, for example, remove computers from the network and restrict access to users, preventing them from having access to confidential information.
There are various devices helping in the communication between nodes, for example:
- Switches: The main purpose of switches is to share information between specific computers without involving the other computers in the network. This means that these computers can continue doing what they are doing. Looking at the following diagram, you will see that by using a switch, Computer A sends a message to Computer B, without the other computers seeing the message. Those computers can send other messages at the same time and without interference.
- Routers: Routers do most of the hard work in a network as they make the decisions about all the messages that pass through the network. This means that they analyse each piece of data and protect information from security threats through a firewall. Routers also choose the route for the data to travel and decide which computer gets priority.
- Wireless access points: These points allow devices to connect to a wireless network without cables. It can also give useful data about the devices on the network.
Activity 9.1
1. Write the correct answer to the questions below in your book:
a. In computer networks, computing devices are called__________?
A. Computers
B. Nodes
C. Modems
D. Switches
b. A PAN is a__________.
A. Network that operates in a large area, such as across a country
B. Network built for a single person connecting all the devices
C. Very small network that usually covers a single home
D. Network that operates in a small area, such as a house, school or office
c. A switch is a device that_______.
A. Shares information between specific computers without involving the other computers in the network
B. Makes the decisions about all the messages that pass through the network
C. Connects a computer or network to the internet
D. Allows computing devices to connect to a wireless network without cables
d. Ethernet___________.
A. Is a set of rules that define the way in which two networking nodes can communicate
B. Is a type of data link protocol that defines the types of cables and connections used to wire computers, switches and routers together
C. Connects a computer or network to the internet
D. Can remove computers from the network and restrict access to users
e. The people who can modify and change the network settings are called the___________.
A. Network technicians
B. Computer nerds
C. Network administrators
D. Gamers
UNIT
9.2 Uses of networks
So far, you have learned that networks can be used in a variety of environments; from schools to businesses to homes. These uses (aims and objectives) can be grouped into the following four main categories:
1. Sharing resources
2. Connecting people
3. Organising information
4. Access to entertainment
In this section, we will look at the different uses of networks, as well as their advantages and disadvantages.
AIMS AND OBJECTIVES OF NETWORKS
Networks have become something that we can barely live without. In this section, we will take a look at some of their main uses.
SHARING
One of the primary objectives of a network is to share information.
Although networks are designed to share information, they do much more than that; they also share the resources linked to the computers on the networks. This includes access to the internet, files, hardware, people and money.
The most common reason for creating a home, school, or office network is to provide all the computers connected to that network, access to the internet. In South Africa, the internet is an expensive resource. By sharing the internet between many people, it becomes slightly more affordable and people who would previously not have had access to the internet, can now gain access.
Something to know
According to the United Nations (UN) agency that oversees international communications, more than three billion people all over the world are using the internet. This number increased from 738 million in 2000, to 3.2 billion in 2015. This is fantastic, right? So now, people from South Africa can send a file, text or image from their computers to someone anywhere in the world with just the click of a button.
The second most common reason for creating a home or office network is to provide access to shared files. In many offices, a central computer or server is used to store shared files and anyone who needs access to these files, can access them through the server.
Homes and offices also use networks to share hardware, such as printers and scanners. This allows many people to use a single printer or scanner without too much hassle or causing any problems.
NETWORKING TO SUCCESS!
At some point you must have come across the terms cloud, cloud computing, or cloud storage, but what exactly is this cloud?
In simple words, the cloud is the internet and refers to all the things you can access remotely through the internet. If a file or folder, or pretty much anything that is stored on the cloud, is stored on internet servers and not on your computer’s hard drive.
People all over the world use the cloud, because it is reliable and convenient. It is easy to store and share files, as well as back-up data. If, for example, you have used an email application, such as Gmail or MWeb mail, you have already used the cloud!
The nice thing about the cloud is that even if your computer crashes, you can still access your information if you have previously backed it up on the cloud.
Have a look at the video link on the left to understand more about cloud computing, it is worth a watch!
When we think of resources, remember these are not just restricted to your computer, but can also extend to real-world resources, for example, people and money. Should you encounter a problem, you can get advice from experts all over the world by asking for advice on the internet. Banking sites, investment sites and crowdfunding websites, such as GoFundMe.com, can provide you with access to money.
WHAT IS THE CLOUD?
ORGANISING INFORMATION
Computer networks not only provide access to information; they also help people to organise information. This could be something small, such as a Google Calendar event where people work together to organise a single event. It can be something complex, such as Google Maps that gives people driving directions in more than 240 countries and covers over 64 million kilometres of road (that is about 83 trips to the moon and back).
By recording information in a central location on a network, people can work together to organise it in a way that is useful and understandable.
CONNECTING PEOPLE
Another important use of networks or telecommunication networks is to connect people. This can be through emails, video calls on your computer, social networks such as WhatsApp or other instant messaging services (IMSs). Using computer networks makes this possible and allows people from anywhere in the world to communicate with one another.
ACCESS TO ENTERTAINMENT
A final important use of networks is to give people access to entertainment. In the past, entertainment was an expensive luxury that only a few people could have. Today, things are different; the average person with an internet connection can watch and listen to a wide variety of films and albums on the internet. In fact, internet access provides access to an almost unlimited amount of entertainment; from books to read, music to listen to, watching the news, or chatting with friends.
ADVANTAGES AND DISADVANTAGES OF NETWORKS
Networks also pose potential advantages and disadvantages. The following table looks at the risks and benefits that come with networks.
Table 9.1: Comparison of the advantages and disadvantages of connecting to a network
Everything has its advantages and disadvantages; it is just the way life goes. However, the table on the previous page is just a list of potential advantages and disadvantages; the way in which you use the network is the only way you get affected, positively and negatively. For example, if you want to learn how to bake, speak a new language or even build your own treehouse, there are always free resources to teach you a new skill. But at the same time, the downside is that the internet also has a dark side. So, what you get from a network depends on what you are looking for and your ability to use it.
THE INTERNET: THE NETWORK OF NETWORKS
We have spoken a lot about networks and how networks enable telecommunication, but what exactly is the driving force behind that? The internet is a global network made up of many, many computers (we are talking about billions of computers) and other electronic devices. You can access almost any information, communicate with anyone anywhere across the world and do much more, just by connecting a computer or electronic device to the internet.
There are also a lot of other things that you can do on the internet. As you know, one of the best things about the internet is how quick it is, and how quickly you can communicate with anyone anywhere in the world. You can email and use social media, you can pay bills, do online shopping, listen to music, meet new people, or even learn a new skill.
WHERE DOES THE INTERNET COME FROM?
UNIT
9.3 Social implications: Networks
There are legal, ethical and security aspects you should take note of with regards to networks. These include viruses, licensing contracts, adhering to the user policies and ownership of electronic material. In this section, we will look at each of these aspects in some more detail.
VIRUSES
This is anyone’s worst nightmare. Without a proper antivirus program installed, you will be prone to getting a virus. Viruses can be transferred through flash disks, or through other computers in a network. Antivirus programs help to protect your software, data and PC from possible threats.
Read through the following case study and discuss the questions in small groups.
Case Study 9.1 Viruses are dangerous
Viruses can be very dangerous. In 2000, there was a virus called the “ILOVEYOU virus”. Although, by today’s standards, it is a pretty silly virus, it still is one of the most well-known and destructive viruses of all time. It even made the Guinness World Record for being the most “virulent” virus of all time. It overwrote both system and personal files, and spread itself over and over again.
The virus was a worm that was downloaded by clicking on an email attachment called “LOVE-LETTER-FOR-YOU.TXT.vbs”. Although people did not know the person sending the email, or the fact that it made headlines around the world, people still clicked on it, activating the virus and attaching it to all their emails.
In the end, the two programmers who developed the virus were caught. Unfortunately, they were set free as there were no laws against writing malware at that time.
Discuss the following in pairs.
1. Will you open an email sent to you from someone you do not know? Motivate your answer.
2. How will you know that something (an email, website, etc.) is dodgy? What would you do in such a case?
3. What can you do to ensure that you do not get a virus like that?
LICENSING CONTRACTS
An organisation cannot just share software over a network, it must purchase a network licence; otherwise, it is illegal. A network licence lets more than one user at a time access the software on the server.
Depending on the number of computers attached to the network, the network licence fee will be different. A legal agreement that lets users install software on a number of computers is called a site licence.
USER POLICIES
Organisations, such as schools and businesses, normally have an acceptable computer usage policy in place. This policy stipulates how computer equipment should be used and prevents anyone from accessing restricted information or data on the network. If a person breaks the rules, it is regarded as a serious offence and the person could get into a lot of trouble.
Something to know
Believe it or not, plagiarism is actually very old; it just was not frowned upon then as it is now. Shakespeare is known to have “borrowed” a lot from other writers. However, back in the day, plagiarising was actually seen as a compliment.
OWNERSHIP OF ELECTRONIC MATERIAL
Accessing data that is not your own is regarded as a criminal offence. For example, you should not change or access the data on the computer of another network user without getting his or her permission. Plagiarism is when you illegally copy information from the internet, or from any other published material and say that it is your own, unless you obtained permission to use it.
Case Study 9.2 Plagiarism in music
The “Blurred Lines case” made the news when Pharrell Williams and Robin Thicke were accused of copying Marvin Gaye’s music to create “Blurred Lines”. This was the most popular song in 2013. Marvin Gaye’s children were awarded US $7.4 million since the jury was in favour of their claims.
Answer the following questions on your own.
1. Why was it seen as plagiarism? What did they do wrong?
2. What do you think about plagiarism – should the law continue working against plagiarism? Why or why not?
Activity 9.2
Miss Furry wants to network the computers and other hardware devices in her office. She shares a printer with three other people. She was told she would need a switch, router and a modem.
1. Define a computer network.
2. Answer the following questions with reference to the scenario above:
a. Give two advantages of creating a network for Miss Furry.
b. List one type of hardware device that she can connect to the network.
c. Is this hardware (your answer for question b above) an input or output device? Motivate your answer.
d. Briefly explain how Miss Furry can use the network to communicate to others.
3. Explain what the internet is.
4. An organisation cannot just share software over a network.
a. Provided that this statement is true. What can an organisation do to share software?
b. Briefly give a description of a network licence.
c. Explain what a site licence is.
REVISION ACTIVITY
1. What is a computer network? (4)
2. Your school is planning to network its 25 stand-alone computers.
a. List two advantages to the school of installing a network. (2)
b. List two disadvantages to the school of installing a network. (2)
c. Apart from a network server and cabling, what other hardware would the school need when installing the network? (2)
3. The diagram below shows a simple network. Use the diagram to answer the following questions:
a. What are A and B? (2)
b. What is device C? There are two possible answers. List both of them. (2)
c. Which device is receiving information? (1)
4. “The internet is an example of a computer network.” It this statement true or false? (1)
5. Reinet is doing research for her PAT. She finds an interesting website on the internet. When she prepares her final presentation, she copies large sections of text from the website and pastes them into her presentation.
a. Is Reinet allowed to copy sections of text into her presentation and pretend that she wrote it herself? Give a reason for your answer. (2)
b. Give one word for what Reinet has done. (1)
TOTAL: [19]
AT THE END OF THE CHAPTER
Use the checklist to make sure that you worked through the following and that you understand it.
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Chapter 8: Extended software concepts
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Chapter 10: Types of networks: PAN/HAN
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