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Edexcel GCSE Computer Science > Topic 5 - Communication and the internet > Flashcards

Topic 5 - Communication and the internet Flashcards

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1
Q

What is a Computer Network?

A

Connections between nodes (devices attached to the network) that allow data to be exchanged.

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2
Q

What is a Local Area Network (LAN) ?

A

A network that connects computers that are close to each other.

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3
Q

What are two examples of places that may use LAN?

A
  1. A house

2. A school

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4
Q

What is a Personal Area Network (PAN) ?

A

A network based around one person.

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5
Q

What are examples of devices used through PAN?

A

Laptop, phone, printer (all connected through wirelessly)

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6
Q

What is a Virtual Private Network (VPN) ?

A

A private network extended across a public network.

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7
Q

Which two types of people might use VPNs and why?

A
  1. Employees - to access a company’s private network from external locations
  2. General users - wanting to hide their browsing.
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8
Q

What is the name of the devices that enables a user to connect to a network?

A

Network Interface Card (NIC)

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9
Q

What is a NIC and what does it do?

A

It is a circuit board that connects to the motherboard and then to the network.

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10
Q

What is the unique identifier called that is manufactured in an NIC?

A

Media Access Control (MAC) Address

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11
Q

What three features does a MAC address contain?

A
  1. It’s 6 bytes long
  2. The first half is the Manufacturer Code.
  3. The second half is the Unique Device Code.
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12
Q

What is the main use of a MAC address?

A

Used through LANs and so do not give the indication of where the device is.

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13
Q

What is a host?

A

A computer connected to a network

i.e. A server connects the computers in a network to provide the Internet

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14
Q

What is a domain name?

A

Refers to the network

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15
Q

What is a hostname?

A

A string of characters that uniquely identifies a computer

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16
Q

What two features does a web address contain?

A
  1. Hostname (e.g. thisisadham)
  2. Domain name (e.g: .rataba.uk)

thisisadham.rataba.uk

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17
Q

What are protocols?

A

Sets of rules for communication between connected machines

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18
Q

What is a network packet?

A

Small amount of data sent over to a computer network. When something is transmitted over a network, it is broken down in packets to be sent. At the final destination, the individual packets are reassembled.

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19
Q

What are the 4 layers of the Internet Protocol Suite (TCP/IP) ?

A
  1. Application Layer
  2. Transport Layer
  3. Network Layer
  4. Link Layer
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20
Q

What does the Transmission Control Protocol (TCP) do?

A

Provides reliable and ordered transfer of data between two devices.

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21
Q

What does the Internet Protocol (IP) do?

A

Specifies the structure of packets and defines addressing.

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22
Q

What is an alternative method to packet switching (sending data in packets) ?

A

Circuit switching

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23
Q

What is circuit switching?

A

Where a single circuit is established and a steady stream is sent.

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24
Q

What are three layers within the structure of a packet?

A
  1. Header
  2. Body
  3. Trailer
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25
Q

What does the Header contain (3) ?

A
  1. The packet number (which packet it is in a sequence of packets)
  2. The MAC and IP Address of the sender and receiver
  3. Which protocol is being used.
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26
Q

What does the Body contain?

A

Contains the actual data being sent.

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27
Q

What does the Trailer contain?

A

May contain a checksum

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28
Q

How does a checksum algorithm work (3) ?

A
  1. Adds together the values of all the data being held in the packet.
  2. Transmits the value as part of the packet (checksum)
  3. When the packet is received, the process can be repeated and then compared. If different, the packet can be resent.
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29
Q

Why are checksums used?

A

To clean up errors during transmission through communication channels

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30
Q

What is the alternative method of error detection during transmission?

A

Parity bit (added to the end of transmission)

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31
Q

What are the two types of parities?

A

Even parity and Odd parity

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32
Q

What does Even Parity mean?

A

The number of 1s in transmission are counted and if there is an odd number of 1s, the parity bit is sent to 1 (making it even) . If there is an even number of 1s, the parity is sent to 0.

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33
Q

What does Odd Parity mean?

A

The number of 1s in transmission are counted and if there is an even number of 1s, the parity bit is sent to 1 (making it odd). If there is an odd number of 1s, the parity is sent to 0.

34
Q

What is a cable (in Network Media) ?

A

Two or more wires running parallel in one assembly which enables the transfer of signals from one device to another.

35
Q

What are the 3 types of Network Media?

A

Copper, Fibre-Optic, Wireless

36
Q

What are the 2 features of Copper Cables?

A
  1. Used because of its high electrical conductivity

2. Data is transmitted down these cables through electrical signals.

37
Q

How does a Fibre-Optic cable work?

A

Uses pulses of light in a transparent core to transmit data. Light is kept in the fibre because it undergoes total internal reflection.

38
Q

What are the three features of Wireless?

A
  1. Networks can be established wirelessly through radio waves.
  2. WiFi is a Wireless Local Area Network (WLAN) based on certain standards.
  3. A wireless Access Point (AP) broadcasts this radio signal which devices detect and join.
39
Q

What is a topology?

A

The arrangements of nodes and connections in a network.

40
Q

What are the 3 types of network topologies?

A

Bus, Ring, Star, Mesh

41
Q

What happens in a Bus Topology?

A
  1. All the clients, servers and resources are connected to one medium (the bus).
  2. When a node communicates, the data is transmitted down the bus which all devices receive, but only the intended recipient accepts and processes the message.
42
Q

What happens in a Ring Topology?

A
  1. Each device is connected to two other devices, which forms a RING for the messages to travel around.
  2. The nodes take turns sending the data, and when a message is sent, it is sent in one direction and is received by each device until the intended recipient receives it.
43
Q

What happens in a Star Topology?

A
  1. Most home network LANs (and WLANs) use this topology as it has a central connection point that could be a router or an AP.
  2. Each node is linked to the central connection point.
44
Q

What happens in a Mesh Topology?

A
  1. Every node is connected to every other node in a network (though in a more practical sense). There are just many connections between nodes.
  2. A full mesh might be used to provide a backup mechanism should one connection fail, because all devices could still be accessed, albeit not directly.
45
Q

What is the Internet?

A

The worldwide connection of networks that uses the Internet Protocol Suite (TCP/IP). The Internet is an example of WAN.

46
Q

What is the Internet maintained and constructed by?

A

Internet Service Providers (ISP) - Large organisations providing services to access and use the Internet.

47
Q

What are the 4 levels of an ISP Hierarchy?

A
  1. Tier-1 ISPs
  2. Tier-2 ISPs
  3. Access ISPs
  4. End systems
48
Q

What are Tier-1 ISPs?

A

A few very large, very fast and high-capacity international networks, operated by large communication companies. These are thought of the CONNECTING BACKBONE of the Internet.

49
Q

What are Tier-2 ISPs?

A

Similar to Tier-1 ISPs, but may be smaller and less international.

50
Q

What are Access ISPs?

A

Provides Internet access to individual users.

51
Q

What are routers?

A

Special purpose computers used for forwarding packets.

52
Q

What does a router maintain?

A

A forwarding table - which contains information about surrounding networks and where the packets should be sent based on their destination address.

53
Q

What does a HOME router do?

A

Connects the user to the ISP

54
Q

What does an powerful CORE router do?

A

Forwards packets along the backbone itself.

55
Q

How does the router know where to send the packets?

A

It uses a destination IP Address to identify where to send the packet. Routing algorithms identify the best route to get it there.

56
Q

What does an IP Address represent?

A

It uniquely identifies a device on a network, and defines where it is located geographically.

57
Q

How many bit numbers are IPv4 addresses?

A

32 bit numbers - allowing it to address 4,294,967,296 (2^32) hosts uniquely.

58
Q

How many bit numbers are IPv6 addresses?

A

128 bit numbers - allowing it to address 3.4x10^38 (2^128) hosts uniquely.

59
Q

What is a Static IP Address?

A

An IP Address that does not change once assigned.

60
Q

What is a Dynamic IP Address?

A

An IP Address that is assigned when connected to a network, so can change.

61
Q

What is a Server?

A

A provider of a service or a resource.

62
Q

What is a Client?

A

A requestor of a service from a server.

63
Q

What is a Peer-to-Peer network (3) ?

A
  1. Has no central server.
  2. Each computer is equal in responsibility than the clients. Each computer has the ability to work as both the client and the server.
  3. Examples of Internet services that use this technology are: Bitcoin and BitTorrent.
64
Q

What is a Domain Name System (DNS) ?

A

A server that translates a non-user friendly IP address to its domain name.

65
Q

What are the stages within a DNS?

A

DNS operates within a client/server network.
In the context of Google:
1. User requests a website. (www.google.co.uk)
2. Request is sent to DNS
3. If the IP Address is in the DNS Server database, then the user can contact domain servers via routers.
4. Google is presented.

66
Q

What is the World Wide Web (WWW)?

A

A portion of the Internet and consists of billions of Linked Web pages written in HTML.
Interent = Hardware and WWW = Information stored on the hardware.

67
Q

What is a Uniform Resource Locator (URL) ?

A

The full address used to locate and retrieve web pages.

68
Q

What is HyperText Transfer Protocol (HTTP) ?

A

The set of rules governing how documents are transferred between the browsers and Web servers.

69
Q

What is HTTPS?

A

An extension of HTTP with added security.

70
Q

What is Hypertext?

A

Forms the basis of simple Web pages.

71
Q

What is Hypertext Markup Language (HTML) ?

A

The language used to create a webpage. It is not a programming language but a markup language so it is used for PRESENTATION.

72
Q

What is Cascading Style Sheet (CSS) ?

A

Used to DESCRIBE the presentation of a HTML document. It makes web pages more attractive to look at. CSS is a way of formatting the HTML document outside the HTML code.

73
Q

In terms of the Internet, what is the client?

A

The Web browser is the client acting ON BEHALF of the user.

74
Q

What are the two types of processing used in the Internet?

A
  1. Client-side

2. Server-side

75
Q

What are the three features of Client-side processing?

A
  1. Interactive Web pages are ‘made’ and things can happen dynamically.
  2. Temporary storage can be interacted with (like Cookies)
  3. Programming on client-side can be done using JavaScript, and HTML/CSS are used.
76
Q

What are the three features of Server-side processing?

A
  1. Permanent storage can be accessed (like using SQL to query databases).
  2. User input can be processed.
  3. Server-side programming languages include C++, Java, C#
77
Q

What is a Script?

A

Set of commands that can be executed without user interaction.

78
Q

What are 2 advantages of Client-side processing?

A
  1. Reduces the workload of the server, which can potentially speed it up.
  2. Allows for more instant responses, e.g. if inputs can be validated by the client, then it saves a ‘trip’ to the server and reduces overall Web traffic.
79
Q

What are 3 advantages of Server-side processing?

A
  1. Servers are usually powerful, and so processing is faster server-side.
  2. No software plugins need to be installed on the user’s computer.
  3. Any patches/updates only need to be applied on the server.
80
Q

What is a Web Cookie?

A

Small piece of data sent from a Web server and stored in the user’s Web browser while the user is browsing. Whenever the browser then requests a page from the server, the data is sent back.

81
Q

What is the main use of a Cookie?

A

To identify the user and prepare customised Web pages for them.

82
Q

What are Tracking Cookies?

A

Cookies that store details of an individual’s browsing histories, often used by advertisers to serve relevant adverts.

Edexcel GCSE Computer Science (6 decks)

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