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

01 Section 2 - Protocols and the Internet Flashcards

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
What does TCP stand for?
Transmission Control Protocol
26
What does IP stand for?
Internet Protocol
27
What does TCP do?
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
28
What does IP do?
Responsible for pack switiching
29
What other protocols build on TCP/IP to do specific Internet based tasks?
``` HTTP HTTPs FTP POP3 IMAP SMTP ```
30
What does HTTP stand for?
Hyper text transfer protocol
31
What does HTTPs stand for?
Hyper text transfer protocol SECURE
32
What does FTP stand for?
File Transfer Protocol
33
What does POP3 stand for?
Post office protocol - version 3
34
What does IMAP stand for?
Internet message access protocol
35
What does SMTP stand for?
Simple mail transfer protocol
36
What is HTTP used for?
Used by web browsers to access websites and communicate with web servers
37
What is HTTPs used for?
A more secure version of HTTP. Encrypts all information sent and received
38
What is FTP used for?
Used to access, edit and move files between devices on a network
39
What is POP3 used for?
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
What is IMAP used for?
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
What is SMTP used for?
Used to send emails. Also used to transfer emails between servers
42
What is a layer in networking?
A group of protocols which have similar functions
43
What are the features of layers within networking?
- layers are self-contained | - each layer serves the layer above it (does the hidden work needed for the layer above)
44
What does layers being self-contained mean?
Protocols in each layer do their job without needing to know what's happening in other layers
45
What are the four layers of networks?
Layer 4 - Application layer Layer 3 - Transport layer Layer 2 - Network layer Layer 1 - Data link layer
46
What do the protocols in the application layer cover?
Turning data into websites and other applications and vice versa
47
What are the protocols in the application layer?
HTTP FTP SMTP
48
What do the protocols in the transport layer cover?
Controlling data flow
49
What are the protocols in the transport layer?
TCP
50
What do the protocols in the network layer cover?
Making connections between networks, directing data packets and handling traffic. Used by routers
51
What are the protocols in the network layer?
IP
52
What do the protocols in the data link layer cover?
Passing data over the physical network. Responsible for how bits are sent as electrical signals over cables, wireless and other hardware
53
What are the protocols in the data link layer?
Ethernet
54
What are the advantages of using layers?
- 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
What is the internet?
A network of networks, a WAN which connects devices and networks from all over the world -based around protocol TCP/IP
56
What is the world wide web(www)?
A collection of websites that are hosted on web servers and accessed through http protocol
57
What are URLs?
Addresses used to access web servers and resources on them
58
What does DNS stand for?
Domain name server
59
What is the DNS's purpose?
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
What is hosting?
When a business uses its servers to store files of another organisations
61
What is the traditional use of the Internet?
For the hosting of websites
62
What is cloud computing or 'the cloud'?
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
What are the pros of cloud computing?
- 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
What are the cons of cloud computing?
- 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
What is a virtual network?
A network that is entirely software-based | -created by partitioning off some of a physical network's bandwidth to form a separate network
66
What are the features of virtual networks?
- 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
What does VPN stand for?
Virtual private network
68
What is a VPN?
A type of virtual network that can be used to send data securely over a large network, like a WAN or the Internet
69
What is a virtual LAN?
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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