OCR J277 GCSE Computer Science > Section 3 Flashcards > Flashcards

Section 3 Flashcards

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1
Q

What is the Internet a world-wide collection of?

A

Inter-connected networks not owned or managed by any one group of people

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2
Q

Who can access the Internet?

A

Anyone

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3
Q

Where is all information on the World Wide Web stored?

A

Documents known as web pages

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4
Q

Is the World Wide Web and the Internet the same thing?

A

No

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5
Q

Where are websites stored?

A

Web Servers connected to the internet

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6
Q

How are web pages accessed?

A

Web Browser

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7
Q

What is the difference between the Web and the Internet?

A
  • Web is one of the ways information is communicated over the Internet
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8
Q

Which is used for email and instant messaging: Internet or the Web?

A

Internet

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9
Q

What does each networked computer have that is unique?

A

IP address

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10
Q

What does an IP stand for?

A

Internet Protocol

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11
Q

What is the difference between IPv4 and IPv6?

A

IPv4 - Current system, Four 8-bit fields, Dotted Decimal Digits
IPv6 - 128 bits, 8 groups of 16 bits, four hexa-decimal digits, separated by colons

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12
Q

What do you type instead of an IP address when you wish to access a site?

A

Domain Name or URL (Uniform Resource Locator)

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13
Q

What happens when a user types a URL?

A
  • URL sent to a local DNS server, translated into IP address
  • If address is found, it is passed back to the browser
  • If not found, it is passed ‘up the chain’ to the next DNS server
  • If it cannot be
    found, an error is passed back and browser displays error message
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14
Q

What are the advantages of using DNS Servers to translate domain names into IP addresses?

A
  • Humans do not have to remember or type numerical address
  • if address changes, DNS can update database, so users continue to use same domain name
  • Many distributed DNS servers so everyone can access all addresses from local DNS Server
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15
Q

What must a computer device have to connect to the Internet?

A

Network Interface Controller (NIC)

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16
Q

What does each NIC have?

A

Media Access Control Address (MAC)
assigned by manufacturer

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17
Q

Can a device have more than one MAC address?

A

Yes, for example, one for wired Ethernet and one for wireless, or one for wireless and one for Bluetooth

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18
Q

How is a MAC address presented?

A

48-bit address written as twelve hex digits, make it easier for humans to work with

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19
Q

What is a WAN?

A

A Wide Area Network that connects computers over a large geographical area using third-party carriers like BT

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20
Q

What is the largest WAN in the world?

A

The Internet

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21
Q

What is circuit switching?

A

A dedicated connection set up between sender and receiver for the duration of communication (used in telephone calls)

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22
Q

What is packet switching?

A

Breaking data into packets that travel independently along different routes and are reassembled at the destination

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23
Q

What information is contained in a packet header?

A

IP address of destination, IP address of source, sequence number, total number of packets, error checking data

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24
Q

What is a LAN?

A

A Local Area Network covering a small geographical area with computers and peripherals connected on a single site

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25
Give three benefits of networking computers
Sharing resources (files/printers), centralised management (user profiles/backups), shared Internet connection
26
Give two disadvantages of networking computers
Managing large networks is complicated and viruses can spread across the entire network
27
What is a star network topology?
A network where all devices connect to a central hub/switch/server with individual cables
28
Give one advantage of a star network
If one cable fails other workstations are not affected
29
Give one disadvantage of a star network
If the central switch or server fails the whole network goes down
30
What is a mesh network?
A network where devices act as nodes with multiple connection paths between them
31
Give two advantages of mesh networks
Self-healing (finds alternative routes if a node fails) and easy to expand by adding new nodes
32
What does a router do?
Routes data packets across networks (WANs) and connects different networks together
33
What does a switch do?
Forwards packets to specific devices on a LAN using MAC addresses and port numbers
34
What is a NIC?
A Network Interface Card required to connect any device to a network (wired or wireless)
35
What is Ethernet?
A family of protocols/rules for formatting and transmitting data on Local Area Networks
36
What is twisted pair copper cable used for?
Connecting devices in LANs - lightweight and inexpensive
37
Give two advantages of fibre optic cable over copper
Greater bandwidth/faster transmission, less signal loss (3% vs 94% over 100m), no electromagnetic interference
38
What is Wi-Fi?
A family of protocols for wireless networking using radio waves
39
What is a WAP?
A Wireless Access Point that converts data into radio waves for wireless transmission
40
Give two risks of wireless networking
Unauthorised access/hacking and bandwidth stealing by intruders
41
What is Bluetooth used for?
Short-range wireless communication (typically up to 10 metres) between devices
42
Give two uses of Bluetooth
Connecting wireless mouse to laptop and linking hands-free headset to smartphone
43
What is encryption?
Converting data into an unreadable format to protect it from unauthorised access
44
What is plaintext?
The original unencrypted message
45
What is ciphertext?
The encrypted message
46
What is symmetric encryption?
Encryption using a single secret key to both encrypt and decrypt messages
47
What is asymmetric encryption?
Encryption using a public key to encrypt and a private key to decrypt (more secure than symmetric)
48
What is a client-server network?
A network where clients request services/resources from a central server
49
Give two advantages of client-server networks
Centralised backup and security controlled centrally
50
What is a peer-to-peer network?
A network where all computers have equal status and share resources directly with each other
51
Give one advantage of peer-to-peer networks
Easy to set up and no expensive server needed
52
Give one disadvantage of peer-to-peer networks
Backup must be done separately for each computer
53
What is cloud storage?
Storing data on remote servers maintained by third parties and accessed via the Internet
54
Give two advantages of cloud storage
Access data from anywhere with Internet and backup is provider's responsibility
55
Give one disadvantage of cloud storage
Dependent on having Internet connection to access data
56
What is bandwidth?
The amount of data that can be transmitted in a given time (measured in Mbps)
57
What is latency?
The time delay between starting transmission and receiving it at the destination
58
Give two factors that affect network performance
Bandwidth available and number of devices connected to the network
59
What is a protocol?
A set of rules that define how devices communicate
60
What is TCP/IP?
Transmission Control Protocol/Internet Protocol - breaks messages into packets and routes them across the Internet
61
What does TCP do?
Defines how messages are broken into packets and reassembled; detects errors and resends lost packets
62
What does IP do?
Identifies device locations on the Internet and routes packets from source to destination
63
What is HTTP?
HyperText Transfer Protocol used for accessing and receiving web pages on the Internet
64
What is HTTPS?
HyperText Transfer Protocol Secure - encrypts web data for secure transmission (used by banks)
65
What is FTP?
File Transfer Protocol used for transferring files between client and server
66
What is POP?
Post Office Protocol - downloads emails from server to local device and deletes from server
67
What is IMAP?
Internet Message Access Protocol - emails stay on server and can be accessed from multiple devices
68
What is SMTP?
Simple Mail Transfer Protocol used for sending emails between mail servers
69
Why are layers used in network protocols?
Creates modular design so each layer handles a specific task; allows easy updates without affecting other layers
70
What does the Application layer do?
Encodes and formats data according to protocols like HTTP or FTP
71
What does the Transport layer do?
Splits data into packets and adds packet numbers for correct reassembly
72
What does the Internet layer do?
Adds IP addresses of sender and recipient to packets
73
What does the Link layer do?
Adds MAC addresses to direct packets to specific devices on a LAN
74
What is a MAC address?
Media Access Control address - unique identifier for a device on a network
75
What is an IP address?
Internet Protocol address - identifies location of a device on the Internet
76
Why is packet switching better than circuit switching for the Internet?
Not enough physical lines for billions of simultaneous dedicated connections; packets can share network resources
77
What happens if a packet arrives corrupted?
Error checking detects the problem and the packet is resent
78
How does a mesh network self-heal?
If one node fails the network automatically finds alternative routes through other nodes
79
What is web hosting?
A service that stores website files on a server and makes them accessible on the World Wide Web
80
What protocol is used to upload website files to a host server?
FTP (File Transfer Protocol)
81
Why might a business use a private WAN?
To connect LANs in different office locations (e.g. London and Leeds) securely
82
What type of cable is cheapest for networking?
Twisted pair copper cable
83
When would you use fibre optic cable instead of copper?
For long distances (over 100m) or high bandwidth requirements or to avoid electromagnetic interference
84
What can cause interference in Wi-Fi transmission?
Cordless phones, microwave ovens, baby monitors, thick walls
85
Why is HTTPS important for online shopping?
It encrypts payment details like card numbers so hackers cannot read the data
86
Which email protocol is best if you check email from multiple devices?
IMAP (because emails stay on the server and sync across devices)
87
Which email protocol downloads emails to one device only?
POP (Post Office Protocol)
88
What is a standard in networking?
Rules that allow hardware and software from different manufacturers to work together
89
Give an example of a network standard
Ethernet protocol or TCP/IP or Wi-Fi standards
90
What size are typical data packets?
Around 512 bytes
91
Why do packets travel along different routes?
To balance network load and avoid congestion; alternative routes available if one fails
92
What happens to packets when they reach their destination?
They are reassembled in the correct order using sequence numbers in packet headers
93
What is a file server?
A server that stores files centrally so authorised users can access them from any network computer
94
What is a certificate authority?
An organisation that issues public and private key pairs for asymmetric encryption
OCR J277 GCSE Computer Science
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