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IGCSE Edexcel Computer Science > Networks > Flashcards

Networks Flashcards

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1
Q

What is a network?

A

An arrangement of two or more computing devices (nodes) connected together in order to communicate with each other and share resources

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2
Q

Give some reasons for connecting computers in a network.

A
  • To share data and software / share hardware peripherals (printers, hard drives, etc.) / share internet connections and services
  • To support collaborative working / provide centralised support and backup services
  • To enable rapid employment of new software and updates / enable people to communicate with each other using services (e.g. email)
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3
Q

Give 3 different types of networks.

A
  • PAN - personal area network
  • LAN - local area network
  • WAN - wide area network
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4
Q

Describe what is meant by a PAN.

A

A network within the range of an individual person

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5
Q

Describe what is meant by a LAN.

A
  • A network in a small area (e.g. a home, school, office building) or group of buildings on a site, existing within a small geographical area
  • Usually managed by local manager or team at site
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6
Q

Describe what is meant by a WAN.

A
  • A network that connects separate LANs over a large geographical area
  • Large companies connect LANs at different sites to share data and resources
  • Managed by several different people or parts of an organisation working together / each LAN could be managed independently
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7
Q

Give 2 network usage models.

A
  • Client-server
  • Peer-to-peer
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8
Q

Describe what is meant by a client-server network.

A
  • A network containing a server that can back up and store data centrally
  • All other devices each considered a ‘client’, may be more than one server
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9
Q

Describe what is meant by a peer-to-peer network.

A
  • A network configuration containing no central server
  • Each device equal in responsibility, each with the ability to work as a client and a server
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10
Q

Name the two network structures that describe the way in which data within the network is transmitted.

A
  • Wired (e.g. via cables)
  • Wireless
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11
Q

State what is meant by ‘range’ in terms of data transmission.

A

The distance over which data can be transferred

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12
Q

State what is meant by ‘bandwidth’ in terms of data transmission.

A

The capacity at which a network can transmit data

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13
Q

State what is meant by ‘latency’ in terms of data transmission.

A

The delay in time between data being transferred and the instruction which caused the transfer

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14
Q

Two types of cables most commonly used for networks are copper wire and fibre-optic cables.

Give some characteristics of copper wire cabling.

A
  • Made of thin copper strands, transmits data as electrical signals
  • High noise contamination
  • Prone to external interference
  • Low bandwidth
  • Easy installation / fairly cheap installation
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15
Q

Two types of cables most commonly used for networks are copper wire and fibre-optic cables.

Give some characteristics of fibre-optic cabling.

A
  • Very low noise contamination
  • Not affected by magnetic interference - data carried using beams of light
  • Secure/reliable data transmission
  • Much higher bandwidth over a longer distance
  • Difficult installation/maintenance
  • Expensive due to cost of electrical components - although does not corrode
  • Made of glass so more fragile
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16
Q

Give some forms of wireless transmission media.

A
  • Wi-Fi
  • Bluetooth
  • Zigbee
  • RFID
  • NFC
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17
Q

Describe the aspects of using wired transmission media to create a LAN.

A
  • Difficult installation - Each device needs own dedicated cable
  • Limited flexibility - Number and location of cable connections is fixed, making changes once set up is likely to disrupt LAN
  • Long range
  • High bandwidth
  • Low latency - Cables have protective coverings, less susceptible to interference
  • Good security - Impossible to tap into physical cables without being in same location as cable
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18
Q

Describe the aspects of using wireless transmission media to create a LAN.

A
  • Easy installation - Adding new devices easy, only WAPs to be connected by cable
  • Versatile - Devices can be moved around without losing connection, new users added easily
  • Short range - Walls and other physical obstacles may obstruct signal
  • Low bandwidth - All active devices must share available bandwidth
  • High latency - Susceptible to interference from other wireless networks or devices
  • Poor security - Anyone within range can intercept transmissions
19
Q

What is meant by ‘network speed’?

A

The rate at which data is transferred within a network

20
Q

What are network speeds measured in?

A

Bits per second, bps

(e.g. Mbps, Gbps)

21
Q

What is the equation to calculate the rate at which data is transferred?

A

Data transfer rate (bps) = File size (bits) ÷ Time (s)

22
Q

Data transfer rate is measured in base-10 units.

Recall the values corresponding to each of the correct units.

A
23
Q

What is a network topology?

A

The way in which devices on a network are physically arranged and connected together

24
Q

Give four examples of network topologies.

A
  • Bus
  • Star
  • Ring
  • Mesh
25
Q

Give some characteristics of a bus topology.

A
  • Each device connected to main communication line called ‘bus’
  • Single cable functions as backbone of network, acting as shared communications medium that all devices connect to via an interface connector
  • When a node communicates, data is transmitted down bus which all devices receive, but only intended recipient accepts and processes message
26
Q

Give some advantages of using a bus topology.

A
  • Easy and cheap to install/set up compared to other wired networks because it only requires a small quantity of cables
  • Easy to add new devices
27
Q

Give some disadvantages of using a bus topology.

A
  • High risk of data collisions occurring when multiple devices transmit data at the same time - devices detect collisions and resend data, slowing down network speed
  • If main cable fails or is damaged, whole network will fail
  • Whole network will fail if a terminator is removed as they ensure data is not caught at ends of bus, ensuring data sent in the correct direction on network
28
Q

Give some characteristics of a star topology.

A
  • All nodes on network connected to a hub
  • Central connection point of a ‘hub node’, could be a device such as a network hub, switch or router
  • (Router on its own cannot be the hub node - needs to be linked to a switch)
29
Q

Give some advantages of using a star topology.

A
  • Data is only sent to the intended computer directly
  • The transmission medium is not shared so there can be multiple simultaneous communications
  • Failure of one node or link doesn’t affect rest of network, it is easy to detect a failure and troubleshoot it as it allows isolation of each device within network
  • It is easy to add new devices without disrupting the network
30
Q

Give some disadvantages of using a star topology.

A
  • If the central point fails, then so will the entire network
  • Increased overall cost of network - requires a lot of cabling because each node connects individually to a central component
  • Performance and number of nodes which can be added depends on capacity of the central device
31
Q

(Exam-style question)

Describe how a star topology is implemented on a wireless LAN. (1)

A

The wireless router acts as a central hub, with individual devices communicating directly with it

32
Q

Give some characteristics of a ring topology.

A
  • Each device has two neighbouring devices
  • Data is passed around in the same direction - either clockwise or anticlockwise
33
Q

Give some advantages of using a ring topology.

A

Messages being sent between two workstations pass through all the intermediate devices, so a central server is not required

34
Q

Give some disadvantages of using a ring topology.

A
  • The failure of any cable within network can cause entire network to crash
  • Maintenance or changes being made to the network nodes can impact the performance of whole network
35
Q

Give some characteristics of a mesh topology.

A
  • Each node connects to at least two other nodes and can connect to every other network node - this arrangement is referred to as being ‘fully connected’
  • It is the most expensive type of network to install
36
Q

Give some advantages of using a mesh topology.

A
  • Mesh networks can heal themselves automatically when a break occurs, so there’s no interruption of service to any node
  • Mesh networks get bigger and faster as more nodes are added
  • Data can be transmitted from different devices simultaneously
  • Can handle high volumes of data traffic as there is always an alternative route for data (e.g. for if one node fails)
37
Q

Give some disadvantages of using a mesh topology.

A
  • This type of network involves more cabling or more wireless devices, leading to higher cost
  • Difficult to manage and requires expert supervision
  • Mesh networks are still in development - a full set of recognised standards have not been adopted yet
38
Q

What is the radio frequency used by smartphones to connect to Wi-Fi?

A

2.4GHz

39
Q

What is 3G?

A
  • It is the third generation of wireless mobile telecommunications technology
  • Allows mobile phones and other devices to connect to internet wherever the device is located, by using a network of phone towers to pass signals
  • Faster data transfer rates than previous generations, enabled mobile devices to access the Internet, and provided greater cybersecurity
40
Q

What is 4G?

A
  • 4G is the fourth generation of mobile phone technology for connecting to/communicating on a network
  • Addresses previous issues of 3G such as the congestion of data on a network and speed - allowed people to use services that demand more capacity, also features reduced latency
  • 4G-enabled devices communicate to the base station (mast) which then relays data from the internet to your device
41
Q

What is 5G?

A
  • The fifth generation of cellular networks - runs on same radio frequencies that are currently being used for smartphones
  • Provides faster connectivity speeds, ultra-low latency and greater bandwidth
  • Greater bandwidth improves quality of internet services in crowded areas
42
Q

(Exam-style question)

Carlo’s smartphone can use 3G, 4G and 5G mobile communication standards.

Give one advantage of using a higher frequency band for mobile communications. (1)

A

Any one from:

  • Higher frequency has more waves per second / carries more data in the same time
  • Higher frequency gives greater bandwidth
  • Higher frequency is more stable / less prone to interference
43
Q

(Exam-style question)

Carlo’s smartphone can use 3G, 4G and 5G mobile communication standards.

Explain one benefit to Carlo of using 5G rather than 3G. (2)

A

Any one from:

  • Gives Carlo faster responses to his communications/connections allowing Carlo to download/share data in a shorter time
  • Gives Carlo more reliable communications/can access communications in more places giving Carlo a better user experience
  • Gives Carlo more secure communications, improving his privacy/reducing other people’s ability to intercept/spy on his communications

IGCSE Edexcel Computer Science (23 decks)

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