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CGP Computer Science > 01 Section 2 - Protocols and the Internet > Flashcards

01 Section 2 - Protocols and the Internet Flashcards

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1
Q

What is a protocol?

A

A protocol is a set of rules for how devices communicate and how data is transmitted across a network

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2
Q

What do protocols cover?

A
  • how communication between two devices should start and end
  • how data should be organised
  • what the devices should do if data goes missing
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3
Q

What addresses do devices use to communicate within a network?

A

MAC addresses

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4
Q

What are MAC addresses?

A

MAC addresses are assigned to all network-enabled devices by the manufacture. They are unique to the device and can’t be changed

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5
Q

What type of numbers are MAC addresses?

A

48 or 64 bit binary numbers

-to make them easier to use they are converted into hexadecimals (6 bite strings)

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6
Q

What protocol uses MAC addresses?

A

Ethernet protocol on LANs

-LAN switches read the MAC addresses and use them to direct data to the correct device

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7
Q

What addresses are used to communicate across networks?

A

IP addresses

-when sending data between TCP/IP networks (e.g. over the Internet)

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8
Q

When are IP addresses assigned?

A
  • Either manually(static) or automatically(dynamic) before the device can access the network
  • aren’t linked to hardware (unlike MAC addresses)
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9
Q

What is a static IP address?

A

Permanent addresses

-on the Internet they can be very expensive

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10
Q

When are static IP addresses used?

A
  • used to connect printers on a LAN

- used for hosting websites on the internet (companies don’t want their websites IP address changing)

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11
Q

What is a dynamic IP address?

A

Addresses that are assigned to a device by a network server

-your device has a different IP address every time you log onto a network

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12
Q

When are dynamic IP addresses used?

A 
By ISPs (internet service providers)
-they are usually more cost effective and can be reused
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13
Q

What type of numbers are IP addresses?

A

32 or 128 bit binary numbers (depending on the version of IP you use)

  • 128 bit are translated into eight hexadecimal numbers
  • 32 bit are translated into four denary numbers
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14
Q

What is data sent between networks split into?

A

Equal sized packets

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15
Q

What do data packets contain?

A
  • a header (containing control information)
  • destination address
  • source address
  • packet number
  • payload
  • checksum number
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16
Q

What is a packet header?

A

The header contains the control information

-control information (like the envelope of a letter) contains the destination address, source address and packet number

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17
Q

What is a packet’s payload?

A

Part of an email, document, web page or streamed video (like the letter inside an envelope)

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18
Q

What is a packet’s checksum number?

A

A form of validation used to check that the payload data hasn’t been corrupted during transit
-the sending and receiving devices both calculate a checksum value by performing a function, if the values match then the data has been received correctly

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19
Q

When is packet switching used?

A

Packet switching is used by routers to direct data packets on the Internet and other IP networks

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20
Q

What is the process of packet switching?

A
  • sending device splits data into packets, and numbers them with a packet number
  • each router reads the packet header, decides which way to send the packet next (according to IP rules)
  • packets take different routes, so can arrive in the wrong order, the receiving device use packet numbers to put them back in the right order
  • if all the data is received and the checksums match, a receipt confirmation is sent to the sending device
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21
Q

What can change the way a packet is sent across a network?

A

The way data is sent across a network changes depending on network traffic so the packets can take different routes.
-if a router receives too many packets at once it may prioritise some over others

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22
Q

What happens if a packet is lost across a network?

A

Sometimes packets can get lost in transit, so the receiving device checks periodically that all the packets have been received. If it hasn’t received them within a certain time, it sends a timeout message back to the sending device.

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23
Q

Why is packet switching an efficient use of a network?

A

There are so many possible routes that data can take, so packets can reach their receiving device even when there’s heavy traffic

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24
Q

What protocol dictates how data is sent between networks?

A

Made up of two protocols

  • TCP
  • IP
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25
Q

What does TCP stand for?

A

Transmission Control Protocol

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26
Q

What does IP stand for?

A

Internet Protocol

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27
Q

What does TCP do?

A

Sets the rules for how devices connect on a network

  • in charge of splitting data into packets and reassembling packets back into original data once it reaches the receiving device
  • responsible for checking data is correctly sent and delivered
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28
Q

What does IP do?

A

Responsible for pack switiching

29
Q

What other protocols build on TCP/IP to do specific Internet based tasks?

A 
HTTP
HTTPs
FTP
POP3
IMAP
SMTP
30
Q

What does HTTP stand for?

A

Hyper text transfer protocol

31
Q

What does HTTPs stand for?

A

Hyper text transfer protocol SECURE

32
Q

What does FTP stand for?

A

File Transfer Protocol

33
Q

What does POP3 stand for?

A

Post office protocol - version 3

34
Q

What does IMAP stand for?

A

Internet message access protocol

35
Q

What does SMTP stand for?

A

Simple mail transfer protocol

36
Q

What is HTTP used for?

A

Used by web browsers to access websites and communicate with web servers

37
Q

What is HTTPs used for?

A

A more secure version of HTTP. Encrypts all information sent and received

38
Q

What is FTP used for?

A

Used to access, edit and move files between devices on a network

39
Q

What is POP3 used for?

A

Used to retrieve emails from a server. The server holds the email until you download it, at which point it is deleted from the server.

40
Q

What is IMAP used for?

A

Used to retrieve emails from a server. The server holds the email until you actually delete it, you only download a copy. Used by most web-based email clients.

41
Q

What is SMTP used for?

A

Used to send emails. Also used to transfer emails between servers

42
Q

What is a layer in networking?

A

A group of protocols which have similar functions

43
Q

What are the features of layers within networking?

A
  • layers are self-contained

- each layer serves the layer above it (does the hidden work needed for the layer above)

44
Q

What does layers being self-contained mean?

A

Protocols in each layer do their job without needing to know what’s happening in other layers

45
Q

What are the four layers of networks?

A

Layer 4 - Application layer
Layer 3 - Transport layer
Layer 2 - Network layer
Layer 1 - Data link layer

46
Q

What do the protocols in the application layer cover?

A

Turning data into websites and other applications and vice versa

47
Q

What are the protocols in the application layer?

A

HTTP
FTP
SMTP

48
Q

What do the protocols in the transport layer cover?

A

Controlling data flow

49
Q

What are the protocols in the transport layer?

A

TCP

50
Q

What do the protocols in the network layer cover?

A

Making connections between networks, directing data packets and handling traffic. Used by routers

51
Q

What are the protocols in the network layer?

A

IP

52
Q

What do the protocols in the data link layer cover?

A

Passing data over the physical network. Responsible for how bits are sent as electrical signals over cables, wireless and other hardware

53
Q

What are the protocols in the data link layer?

A

Ethernet

54
Q

What are the advantages of using layers?

A
  • breaks network communication into manageable pieces - helps developers concentrate on only one area of the network without worry about others
  • layers are self-contained, so can be changed without affecting other layers
  • set rules for each layer forces companies to make compatible, universal hardware and software
55
Q

What is the internet?

A

A network of networks, a WAN which connects devices and networks from all over the world
-based around protocol TCP/IP

56
Q

What is the world wide web(www)?

A

A collection of websites that are hosted on web servers and accessed through http protocol

57
Q

What are URLs?

A

Addresses used to access web servers and resources on them

58
Q

What does DNS stand for?

A

Domain name server

59
Q

What is the DNS’s purpose?

A

It translates a website’s domain name into its IP address
-the internet has a network of domain name servers so you don’t need to remember IP addresses to access websites, you can use the domain names instead

60
Q

What is hosting?

A

When a business uses its servers to store files of another organisations

61
Q

What is the traditional use of the Internet?

A

For the hosting of websites

62
Q

What is cloud computing or ‘the cloud’?

A

Internet hosting for general storage of user files and also providing online software
-acts like an extension of a traditional client-server network where user files are stored centrally on a network server

63
Q

What are the pros of cloud computing?

A
  • users can access files from any connected devices
  • easy to increase how much storage is available
  • no need to buy expensive hardware to store data
  • no need to pay IT staff to manage hardware
  • cloud host provides security and back ups for you
  • cloud software will be updated automatically
64
Q

What are the cons of cloud computing?

A
  • need connection to the Internet to access files
  • dependent on host for security and back-ups
  • data in the cloud can be vulnerable to hackers
  • unclear who has ownership over cloud data
  • subscription fees for using cloud storage and software may be expensive
65
Q

What is a virtual network?

A

A network that is entirely software-based

-created by partitioning off some of a physical network’s bandwidth to form a separate network

66
Q

What are the features of virtual networks?

A
  • several can exist on the same physical network
  • all share the same hardware (virtual networks are more efficient than physical networks)
  • each virtual network has its own security
  • can only be accessed by using a certain software or login information
67
Q

What does VPN stand for?

A

Virtual private network

68
Q

What is a VPN?

A

A type of virtual network that can be used to send data securely over a large network, like a WAN or the Internet

69
Q

What is a virtual LAN?

A

A virtual LAN allows you to split a LAN into several separate networks using the same hardware

CGP Computer Science (24 decks)

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