Skip to content
Cambridge IGCSE0417

Networks

Information Communication Technology 0417 Chapter Notes

What this chapter covers

NetworksNetwork issues and communication
ShareWhatsAppPost
Networks notes

Read online free. Download a watermarked copy with a free account.

Read the notes

The full Networks notes as text: skim, search, and jump between subtopics.

~17 min read

In this chapter

  1. 1Router
  2. 2Network devices: NIC, hub, bridge and switch
  3. 3Wi-fi and Bluetooth
  4. 4Cloud computing
  5. 5Internet, intranet and extranet
  6. 6LAN and WLAN
  7. 7Wide Area Network
  8. 8Privacy and confidentiality of data transfer
  9. 9Strong and weak passwords
  10. 10Protecting passwords from interception
  11. 11Other authentication methods
  12. 12Biometric methods
  13. 13Anti-malware software
  14. 14Video-conferencing
  15. 15Audio-conferencing and web-conferencing

1. Router

A router connects networks and devices to the internet. It connects a LAN to a WAN. It receives data packets and sends them on towards their destination.

A router stores computer addresses in a routing table. It reads the IP address in each data packet and uses the table to work out the best route.

Read the question for whether the network is connected to the internet. If it is not, do not answer as though a router is needed.

Examiner insight

“The concept of routing tables was rarely mentioned.” “Better candidates clearly described the use of the routing table and highlighted the way the IP address is used to work out the best route.”

Worked example 14 marks

A school network is connected to the internet by a router. Describe how the router deals with a data packet.

  1. 1

    The router receives the data packet [1]

  2. 2

    It reads the IP address in the packet [1]

  3. 3

    It looks up the address in its routing table, where it stores computer addresses [1]

  4. 4

    It works out the best route and sends the packet on [1]

2. Network devices: NIC, hub, bridge and switch

A network interface card (NIC) is needed for a computer or device to access a network. It uses a MAC address. Connecting to the internet is the job of a router, not a NIC.

A switch helps form a LAN. It sends data to a specific device. A hub is a different network device, and it is not a central computer. Do not give hub where the answer is switch.

A bridge connects two LANs together. Do not confuse it with a router, which connects a LAN to a WAN.

Examiner insight

“Those candidates that did well on this question clearly identified the need of a NIC for a computer or device to access a network and the use of a MAC address.” “Some candidates thought that the network switch turned the network on and off.”

Worked example 13 marks

An office has a LAN. State the name of the device that sends data only to the computer it is meant for. Explain why each computer needs a network interface card.

  1. 1

    A switch [1]

  2. 2

    The NIC is needed for the computer to access the network [1]

  3. 3

    The NIC uses a MAC address [1]

3. Wi-fi and Bluetooth

Wi-fi and Bluetooth are similar: both are wireless, and both send and receive data packets. They differ in that wi-fi has a faster data transfer rate. The range of the signal is another point to compare.

To connect a device to a network using wi-fi, a password must be entered. Writing only that the device and the wi-fi are turned on is not enough.

To connect a device using Bluetooth, switch Bluetooth on, keep the devices close to each other, then select the device in the list so that the two pair. A password may be required.

Examiner insight

“Candidates gave more differences between WiFi and Bluetooth, but similarities were less well identified.” “many candidates went into technical details about the different channels and hopping between channels which showed a good knowledge of how it works but it did not answer the question.”

Worked example 13 marks

A student wants to connect a pair of wireless headphones to a computer using Bluetooth. Describe the steps the student takes.

  1. 1

    Switch on Bluetooth in the computer [1]

  2. 2

    Make sure the devices are close to each other [1]

  3. 3

    Click on the headphones in the list of devices so that the two pair [1]

4. Cloud computing

In cloud computing, data is stored on remote servers. The data is managed by a third party cloud provider. The user logs in to a cloud account to upload and download files.

The user pays a subscription for the storage, and pays more if more is needed. A portable SSD could be lost or damaged, and has to be carried. Cloud data can be accessed from anywhere, but only with an internet connection.

Hacking on its own is too vague as an issue, because it is true of any server. Give the reason it matters more for the cloud: the data is copied to other servers many times and stays there for a long time.

Examiner insight

“Other candidates thought that the data was stored on the internet, which is too vague an answer as the internet is only infrastructure.” “Some candidates stated that it ‘needs internet’ which does not achieve credit without stating internet connection.”

Worked example 14 marks

A student keeps homework files in cloud storage instead of on a portable SSD. Explain what is meant by the cloud and describe two advantages of using it instead of the SSD.

  1. 1

    In the cloud, data is stored on remote servers [1]

  2. 2

    The data is managed by a third party cloud provider [1]

  3. 3

    Advantage: the student does not need to carry the SSD [1]

  4. 4

    Advantage: the SSD could be lost or damaged, and the files with it [1]

5. Internet, intranet and extranet

The internet is a wide area network. It is available for all to use and contains more information than an extranet. The web is a collection of websites. It is accessed using the internet.

An intranet is private and more secure than the internet. It is used within a company.

An extranet is also a private network, but its users can include vendors and customers. It is restricted to members of the organisation and authorised users.

Examiner insight

“The better candidates made a good comparison in that the internet contained more information and was available for all to use whereas the extranet was restricted to members of the organisation and authorised users.” “As the question related to the extranet some candidates mixed up internet with intranet.”

Worked example 13 marks

A company lets its vendors and customers log in to a private network. Compare this extranet with the internet.

  1. 1

    The extranet is a private network, but the internet is available for all to use [1]

  2. 2

    The extranet is restricted to authorised users, such as vendors and customers, but anyone can use the internet [1]

  3. 3

    The internet contains more information than the extranet [1]

6. LAN and WLAN

A WLAN is a Wireless Local Area Network. It is a group of connected devices using radio transmissions, usually within a building. A LAN is a Local Area Network.

In a WLAN, devices share resources and are easier to connect. There are fewer wires, so it costs less, devices can be positioned more flexibly and there are fewer cables to trip over.

The drawbacks are interference from objects that affect the signal, and a data transfer rate that could be slower than a LAN.

Examiner insight

“Many candidates were able to name the networks but not expand upon this with good, detailed descriptions.”

Worked example 14 marks

A WLAN is a type of network.(b) State the benefits and drawbacks of using a WLAN.

  1. 1

    Benefit: devices can share resources with all devices connected [1]

  2. 2

    Benefit: less cost as there are fewer wires [1]

  3. 3

    Drawback: interference from objects that affect the signal [1]

  4. 4

    Drawback: the data transfer rate could be slower than a LAN [1]

7. Wide Area Network

A WAN is a connection of a number of LANs. It covers a large geographical area and uses a router.

WANs can be private or public. A private WAN can be set up by an organisation to connect its LANs, by leasing telephone lines or using a Virtual Private Network (VPN).

Examiner insight

“A few candidates did not give enough detail in their answers for example a connection of a number of networks was not sufficient as it needs to mention LANs.” “Some candidates discussed the Internet in their answer instead of looking at WANs in general, this was not a sufficient explanation as the Internet as a type of WAN was given in the question.”

Worked example 14 marks

The internet is a type of Wide Area Network.(a) Describe the characteristics of a Wide Area Network.

  1. 1

    It is a connection of a number of LANs [1]

  2. 2

    It covers a large geographical area [1]

  3. 3

    It uses a router [1]

  4. 4

    It can be private or public [1]

Recap

  • Router: connects networks and devices to the internet, stores addresses in a routing table, uses the IP address to work out the best route for each data packet.
  • NIC: needed for a device to access a network, uses a MAC address.
  • Switch: helps form a LAN, sends data to a specific device. Bridge: connects two LANs together.
  • Wi-fi and Bluetooth: both wireless, both send and receive data packets. Wi-fi has the faster data transfer rate.
  • Bluetooth: switch on, keep devices close, select from the list to pair.
  • Cloud: data on remote servers, managed by a third party cloud provider, needs an internet connection and a subscription.
  • Internet: available for all to use. Intranet: private, within a company. Extranet: private, authorised users such as vendors and customers.
  • WLAN: wireless, radio transmissions, usually within a building. WAN: a connection of LANs over a large geographical area, uses a router.

8. Privacy and confidentiality of data transfer

Data sent across a network can be intercepted on its way. The transfer must be kept private and confidential.

Encryption protects the data. It scrambles the data to make it meaningless to hackers. Keys are needed to encrypt the data as well as to decrypt it. Be precise: say what is scrambled and how the keys are used.

Examiner insight

“Most candidates know about the scrambling of data and many seem to realise you need keys to encrypt the data as well as decrypt it.” “Some candidates thought that a firewall stopped hacking on a system but did not explain this fully and therefore could not gain marks.”

Worked example 13 marks

A company sends customers' bank details across a network. Explain why the company should encrypt the data.

  1. 1

    The data can be intercepted while it is sent. [1]

  2. 2

    Encryption scrambles the data, making it meaningless to hackers. [1]

  3. 3

    An encryption key and a decryption key are used, so only someone with the key can read the data. [1]

9. Strong and weak passwords

A weak password is easy to guess. It may be too short, or it may contain personal data.

A strong password uses a range of characters and includes symbols. Writing only that a password is 'not strong' is not enough: say why. Give your own example of each kind: an example copied from the question earns nothing.

Examiner insight

“Some candidates copied the examples given in the question, which could not gain credit.” “Many candidates did not recognise the focus of the question which was to minimise the possibility of passwords being misused if intercepted, so after the event.”

Worked example 14 marks

A user's password is her first name followed by her year of birth. Describe why this is a weak password and what makes a password strong. Include an example of a strong password.

  1. 1

    It is easy to guess. [1]

  2. 2

    It contains personal data. [1]

  3. 3

    A strong password uses a range of characters, including symbols. [1]

  4. 4

    Example of a strong password: `Tr4!ke_92`. [1]

10. Protecting passwords from interception

Key-logging software intercepts a password as it is entered. It still operates when a touchscreen is used. Up-to-date anti-spyware is used to avoid this interception.

A password should also be changed regularly, so an intercepted password cannot go on being misused. The drawback is that a user could forget the new password and be locked out of the system.

Read the question. If the password has already been intercepted, advice on choosing a strong password does not answer it.

Examiner insight

“Key-logging software will still operate even if a touchscreen is used.” “The best answer that the candidates gave was that the user could forget the password and would then be locked out of the system.”

Worked example 13 marks

An employee's password could be intercepted as she enters it. Describe how the company can avoid this and limit the misuse of a password that has been intercepted.

  1. 1

    Use up-to-date anti-spyware to avoid the password being intercepted. [1]

  2. 2

    Employees change their passwords regularly. [1]

  3. 3

    An intercepted password can then no longer be used. [1]

11. Other authentication methods

A password is one authentication method. The syllabus lists others: zero login, biometric methods, magnetic stripes, smart cards, physical tokens and electronic tokens.

Biometrics counts as one method, however many body features it uses. A smart card is a contactless card. A magnetic stripe card is not contactless, and it does have some security.

An example given in the question, such as a password, is there to help you. Do not repeat it as one of your answers.

Examiner insight

“Some candidates wrote down three different types of biometrics but as biometrics is an example of one authentication technique, they limited their marks.” “Many believed that magnetic stripe cards were contactless or that they had no security.”

Worked example 13 marks

A password is one way to authenticate a user. State three other authentication methods.

  1. 1

    Biometric method, for example fingerprint. [1]

  2. 2

    Smart card. [1]

  3. 3

    Physical token (or electronic token, zero login or magnetic stripe). [1]

12. Biometric methods

Biometric data is unique to a person and is always with you. Examples are a fingerprint or a face. The owner has to be present, and biometric data is more difficult to forge than a password. It is not impossible to forge.

A biometric system can fail to operate. Facial hair and poor lighting can stop face recognition. Once set, a biometric is difficult to change.

Examiner insight

“The only common misconception being that biometric data is impossible to forge.” “Common answers included that biometric systems used unique data but failed to explain that it was difficult to change a biometric password once set.”

Worked example 14 marks

A laptop logs a user in by face recognition. Describe two advantages and two drawbacks of this method.

  1. 1

    Advantage: a face is unique to the user. [1]

  2. 2

    Advantage: it is always with the user. [1]

  3. 3

    Drawback: facial hair can stop the system recognising the user. [1]

  4. 4

    Drawback: poor lighting can stop the system operating. [1]

13. Anti-malware software

Anti-malware and anti-virus software scans files and compares them with a database of known viruses. When it detects that a file contains a virus, it removes the virus or quarantines the file.

Scan the storage media used to transfer data, and scan data and software when downloading. Say that the software is up to date: examiners gave a mark for it. A firewall or anti-spyware does not do this job.

Examiner insight

“Many candidates gave answers that were limited to statements that anti-virus software protects against viruses and anti-malware protects against malware.” “Some candidates confused antivirus with anti-spyware.”

Worked example 14 marks

A teacher plugs a USB drive into a school computer and downloads a worksheet. Describe how anti-malware software protects the computer.

  1. 1

    It scans the storage media used to transfer data. [1]

  2. 2

    It scans the data when it is downloaded. [1]

  3. 3

    It compares the files with a database of known viruses to detect a virus. [1]

  4. 4

    Up-to-date software removes the virus or quarantines the file. [1]

14. Video-conferencing

Video-conferencing is used with the internet and uses live audio and video streaming. It is not making a video and sending it to the others.

It saves the costs of travel and the time spent travelling. 'Cheaper' or 'saves time' alone earns nothing. Drawbacks need the same detail: 'additional equipment is expensive' earns the mark, 'equipment is expensive' does not. Time zones and the signing of documents are also issues.

Examiner insight

“Some candidates still write about video conferencing involving making a video and then sending it to the other members of the group.” “For example, 'lip sync problems' would not achieve a mark on its own but expanding on the answer to explain lip sync would have ensured a range of marks.”

Worked example 14 marks

A company with offices in three countries holds a monthly video-conference. Describe what video-conferencing is and give one benefit.

  1. 1

    It is used with the internet. [1]

  2. 2

    It uses live audio streaming. [1]

  3. 3

    It uses live video streaming. [1]

  4. 4

    Benefit: it saves the costs of travel, because staff do not travel to one office. [1]

15. Audio-conferencing and web-conferencing

Audio-conferencing uses the voice. Say more than that. When asked for its advantages, compare it with video-conferencing.

Web-conferencing is an online conference. Use the generic name, never a named software app. It saves transport costs and time, and it can be held anywhere.

Examiner insight

“Some candidates gave proprietary answers rather than generic answers for the audio-conferencing app even though it is clearly written on the question paper not to do this.” “Common correct answers were that the conference would save transport costs and time and also it could be held anywhere.”

Worked example 14 marks

A company holds a web-conference with staff in three countries. Describe two benefits of this instead of a meeting in one room.

  1. 1

    It saves transport costs. [1]

  2. 2

    Staff do not pay to travel to the meeting. [1]

  3. 3

    It saves time. [1]

  4. 4

    No time is spent travelling to the meeting. [1]

Recap

  • Data sent over a network can be intercepted. Encryption scrambles it, and keys are needed to encrypt and decrypt it.
  • Weak password: easy to guess, too short, contains personal data. Strong: a range of characters, including symbols.
  • Avoid interception with up-to-date anti-spyware. Change passwords regularly so an intercepted one cannot go on being used.
  • Authentication methods: zero login, biometrics, magnetic stripes, smart cards, physical and electronic tokens. Biometrics is one method.
  • Anti-malware scans downloads and storage media, detects a virus, then removes or quarantines it. It must be up to date.
  • Video-conferencing is used with the internet and uses live audio and video streaming.
  • Always use the generic name for a conference type. A brand name earns no mark.

End-of-chapter exercise

Test yourself on the whole chapter. Work through these before moving on.

  1. State the name of the network device that connects a network to the internet.1 mark
  2. The internet is a type of Wide Area Network. State two other types of computer network.2 marks
  3. State the purpose of a network interface card in a computer. Give the type of address it uses.2 marks
  4. A school network uses a switch. Describe what the switch does.2 marks
  5. Explain what is meant by the cloud.2 marks
  6. A photographer stores photos in the cloud rather than on a portable SSD. State one benefit and one drawback of using the cloud.2 marks
  7. Describe how a user connects a Bluetooth speaker to a tablet.3 marks
  8. Compare wi-fi and Bluetooth. Give two similarities and one difference.3 marks
  9. A museum has a LAN in each of its two wings. It wants to join the two LANs so that staff can share files. The network will not be connected to the internet. A technician advises: 'Buy a router to join the LANs. The computers are connected by cables, so they do not need network interface cards.' Name the device that should join the two LANs and explain why a router is not needed. Then correct what the technician says about network interface cards, giving a reason.4 marks
  10. A furniture company has an office LAN in each of three cities. It plans to link the three LANs for its own staff only, to let its suppliers log in to check orders, and to keep its order files in cloud storage. A manager writes that the issue with cloud storage is that 'it can be hacked'. State the type of network formed when the three LANs are linked, and describe how the company can keep it for its own use. Name the type of network the suppliers log in to, and explain how it differs from the internet. Explain why the manager's statement would not earn a mark, and improve it.6 marks
  11. A hospital sends patient records across a network. Explain why the records should be encrypted.2 marks
  12. A user's password is `Maya2010`, her name and year of birth. Give two reasons it is weak.2 marks
  13. An attacker has intercepted a user's password. Explain how changing passwords regularly reduces the harm.2 marks
  14. A user says key-logging software cannot intercept her password, because she enters it on a touchscreen. State whether she is correct, and state what she should use to avoid interception.2 marks
  15. A password is one authentication method. State three other methods.3 marks
  16. A phone is unlocked by a fingerprint. Describe two advantages of this over a password.4 marks
  17. A student downloads a game to a home computer. The anti-virus software reports that the file has been quarantined. Describe what the software did to the file, and state one thing that must be true of the software for this to work.4 marks
  18. A firm in London holds a web-conference with a team in Delhi. Describe two benefits compared with a meeting in one room.4 marks
  19. A courier firm's drivers log in to a tablet in their vans, often at night. Their passwords are strong and must be changed every month. The manager wants face recognition instead and says, 'A face is impossible to forge, so nothing can go wrong.' Discuss the manager's proposal. Give points for and against it.6 marks
  20. The three partners of a law firm work in Lagos, Lima and Seoul. Each month they fly to one office to agree and sign contracts. A trainee writes: 'Use video-conferencing. Each partner makes a video and sends it to the others. It is cheaper. A drawback is that equipment is expensive.' Correct the trainee's description of video-conferencing. Then rewrite the benefit and the drawback so that each would earn a mark, and describe two further drawbacks for this firm.6 marks

Go deeper

Practise and revise with member-only material for this chapter.

Workbook

Exam-style practice questions with full worked solutions.

Unlock with a plan

Chapter at a Glance

A single-page summary of every key idea for fast revision.

Unlock with a plan

Free notes are just the start.

Unlock every Workbook and Chapter at a Glance, and generate your own worksheets and predicted papers.

Explore plans

Related chapters

Hardware and softwareInput devices and their usesStorage devices and mediaMicroprocessor-controlled devicesCommunicationAnalysis