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GCSE Computer Science > 1.3 Networks, connections, and protocols > Flashcards

1.3 Networks, connections, and protocols Flashcards

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1
Q

Networks: Advantages

A

1) Users can share files
2) Users can access their files from any computer on the network
3) Servers can control security, software updates and backup of data
4) Communication with other people (e.g. email and social networking)

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2
Q

Networks: Disadvantages

A

1) Increased security risks to data
2) Malware and viruses spread very easily between computers
3) If a server fails, the computers connected to it may not work
4) The computer may run more slowly if there’s a lot of data travelling on the network

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3
Q

What is a LAN (local area network)?

A

1) Covers a small geographical area located on a single site
2) All the hardware for a LAN is owned by the organisation that uses it

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4
Q

How are LANs connected?

A

LANs are either wired (with Ethernet cables, UTP cables, or fibre optic) or wireless (using Wi-fi)

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5
Q

Examples of LANs

A

Examples are businesses, schools and universities.
LANs connect devices such as PCs, tablets, smart TVs, and printers.

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6
Q

What is a WAN (wide area network)

A

1) Covers a large geographical area, connecting LANs together
2) Infrastructure between the LANs is leased (hired) from telecommunication companies who own and manage it

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7
Q

How are WANs connected?

A

WANs are connected with telephone lines, fibre optic cables or radio links

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8
Q

Examples of a WAN

A

An example is the Internet.
Devices connecting to the internet are multifunction, all-in-one devices such as: switch, router, wireless access point (WAP)

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9
Q

What are the 5 factors which affect the performance of networks?

A

1) Bandwidth
2) No. of users
3) Transmission media
4) Error rate
5) Latency

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10
Q

Performance of networks: bandwidth

A

The amount of data sent and received successfully in a given time. The greater the bandwidth, the better the performance.

Measured in bits per second, often called bit rate

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11
Q

Performance of networks: no. of users

A

Too many users or devices on the same network can cause congestion and slow the network if there is insufficient bandwidth (bandwidth is shared). You can limit the amount of bandwidth available to individual users to address this.

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12
Q

Performance of networks: transmission media

A

Wired connections are faster and more reliable (and have a higher bandwidth) than wireless connections. Fibre optic cables can give a better performance (and have a higher bandwidth) than copper cables.

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13
Q

Performance of networks: error rate

A

Less reliable connections increase the number of errors that occur when data is transferred.

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14
Q

Performance of networks: latency

A

The delay from transmitting data to receiving it, caused by bottlenecks in the infrastructure of the network (e.g. not using switches to segment traffic on a network). Hardware such as switches and transmission media may not operate at the same speed
-> hardware other than cables and network topology also have a big effect

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15
Q

What is a client-server?

A

A client-server is managed by a server. The devices connected to the server are clients. Files and software are stored centrally (on the server rather than on individual client devices)

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16
Q

What happens in a client-server model?

A

1) A client makes requests to the server (asking for data and connections)
2) The server processes the requests and responds
3) This is the client-server relationship
4) The server stores user profiles, passwords, and access information (it may request a password/deny requests)

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17
Q

What does a server do in a client-server model?

A

A server controls access and security to one shared file store, manages access to the Internet, manages printing jobs, provides email services, and runs a backup of data

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18
Q

Example of a client-server model

A

Most uses of the Internet work on a client-server relationship (e.g. websites, web browsers are client programs which send requests to web servers)

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19
Q

Advantages of a client-server model:

A

1) Easier to keep track of files as they’re stored centrally
2) Easier to perform backups
3) Easier to install and update software (to all computers)
4) Servers are reliable and always on
5) Easier to manage network security

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20
Q

Disadvantages of a client-server model:

A

1) Expensive to set up and maintain
2) Requires IT specialists to maintain
3) Server dependence - the server is a single point of failure (if the server goes down, all clients lose access to their work)
4) Users will lose access if the server fails
5) Server can become overloaded (too many clients using at once)

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21
Q

What is a peer in a peer-to-peer network?

A

A peer is a computer on the network and equal to all other peers

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22
Q

What is a peer-to-peer network?

A

A network where all devices are equal and connect directly to each other without a server

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23
Q

What do peers do in a peer-to-peer network?

A

1) Serve their own files to each other
2) Each is responsible for its own security and backup
3) Peers usually have their own printers

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24
Q

Examples of a peer-to-peer network:

A

Peer-to-peer networks can be used at home to share files between devices or connect devices to a printer (but the peer would need to be turned on to communicate with the connected printer)
-> common peer-to-peer applications are video calling and (illegal) file sharing

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25
Advantages of a peer-to-peer network:
1) Easy to maintain (no specialist staff needed) 2) No dependency on a server (if one device fails, the whole network isn't lost) 3) Cheaper to set up 4) No expensive hardware needed
26
Disadvantages of a peer-to-peer network:
1) The network is less secure 2) Users need to manage their own backups 3) Can be difficult to maintain a well ordered file store
27
Hardware in a LAN: Network Interface Controller/Card (NIC)
Connects a device to a wired or wireless networking connection. An NIC uses a protocol to ensure successful communication (used to be separate cards but now built into motherboard)
28
What are the advantages and disadvantages of Wireless Access Points (WAPs)
1) Allow wireless-enabled devices to access the network 2) Wireless connections are popular because they avoid the need to install cables 3) Bandwidth on a wireless connection is lower than a wired network 4) Security is more of a problem than wired (more convenient, connection is not as strong/reliable)
29
Hardware in a LAN: Switch
*Sends data between devices on a LAN*. A switch uses the NIC address on a device to route traffic (they segment the network by forwarding traffic to the correct location, switches receive data - in units called frames - from one device and transmit this data to the device on the LAN with the correct MAC address)
30
Hardware in a LAN: Router
*Sends data between networks.* Needed to connect a LAN to a WAN. A router uses the IP (Internet Protocol) address on a device to route traffic to other routers (on the Internet, routers direct data - in units called packets) to their destination, used in homes and offices to connect the LAN to the Internet)
31
Hardware in a LAN: Copper Cables (UTP)
1) Connections between desktop computers and a switch are usually made with unshielded twisted pair (UTP) copper cables. 2) Cheap and flexible so easy to install 3) (wired connected ensure maximum bandwidth, security and reliability, wires are twisted for transmission and receiving, quality of cable affects bandwidth)
32
Hardware in a LAN: Fibre Optic
1) Transmit data as light. 2) High performance and expensive 3) (long distance cables and) WANs are connected with fibre optic cable 4) Has a higher bandwidth than copper cables and doesn't suffer from interference -> Backbone of the Internet uses fibre optic cables, transmit over very large distances without loss of signal quality
33
What is the Internet?
The Internet is a worldwide collection of computer networks (the Internet is a network of computer networks). It's a WAN which connects devices and networks from all over the world (based on the protocol TCP/IP (transmission control/internet protocol))
34
Internet: what is a Domain Name Service (DNS)?
1) A Domain Name Service is made up of multiple Domain Name Servers 2) A Domain Name Service is used to translate website domain names (the URL (Uniform Resource Locator)) into IP addresses for routers (these services use a network of Domain Name Servers which store IP addresses and matching domain names)
35
What is a DNS' role in the conversion of a URL to an IP address? [8]
1) The URL is received by a DNS resolver server 2) The (resolver) server then queries a DNS root name server 3) The root server responds with the address of the top-level domain server for .com 4) The resolver then makes a request to the .com TLD server 5) The TLD server then responds with the IP address of the domain's name server, google.com 6) Lastly, the recursive resolver sends a query to the domain's name server (authoritative name server) 7) The IP address google.com (8.8.8.8) is then returned to the resolver from the name server 8) The DNS resolver then responds to the web browser with the IP address of google.com
36
Internet: what is hosting?
1) Websites are stored on servers dedicated for DNS -> this is known as hosting 2) Hosted solutions provide 24/7 access, multiple users, and greater security
37
Internet: what is the cloud?
1) The cloud is a remote service provision (e.g. storage, software, processing) 2) Servers that store data and programs remotely that can be accessed and used over the Internet are referred to as cloud storage 3) They provide access to anything, anywhere, automatic back up, and collaboration of documents
38
Internet: Advantages of Cloud Storage
1) Access from any device 2) A large storage capacity 3) Automatic backup and updates 4) Easy online collaboration 5) No need for expensive hardware or IT staff
39
Internet: Disadvantages of Cloud Storage
1) Need connection to the Internet 2) Dependent on host for security and backups 3) Data on the cloud is vulnerable to hackers 4) Unclear who has ownership over cloud data 5) Subscription fees for cloud storage and software may be expensive
40
Internet: What do web servers and clients do?
Web servers carry out many functions, especially hosting websites and dealing with client requests.
41
Internet: How do web servers and clients work?
1) URL request by browser made from user (e.g. www.bbc.co.uk) 2) The browser sends the domain (website) name to a Domain Name Server (DNS) 3) The DNS maps the domain name to an IP address and returns it to the browser 4) GET request for the webpage/resource is sent to the web server using the IP address 5) Requested webpage/resource is returned to the client's web browser
42
Internet: what is the role of web servers and clients?
1) Servers provide services (e.g. web server -> web pages, file server -> file storage/retrieval) 2) Clients request/use services from a server
43
What happens in a star network topology?
1) All devices are connected to a central switch or server that controls the network 2) Most popular type of network (can be wired or wireless) 3) The central switch allows many devices to access the server simultaneously. It is intelligent and ensures that traffic only goes where it is intended
44
Advantages of a star network topology:
1) If a single cable is broken, only that computer is affected (the rest of the network is unaffected) 2) It's simple to add more devices to the network 3) Better performance than other setups (devices can transmit data all at once and have few data collisions)
45
Disadvantages of a star network topology:
1) The switch is a serious point of failure (if there's a problem with the switch/server, the whole network is affected) 2) In wired networks, every device needs a cable to connect to the central switch/server (expensive, e.g. for office buildings with 50 terminals)
46
What is a full mesh network topology?
Each device is connected to every other device
47
Advantages of a full mesh network topology:
1) No single point of failure 2) If one device fails, the data is sent along a different route to get to its target
48
Disadvantage of a full mesh network topology:
1) Expensive -> a lot of cabling and switch hardware is required (adds to cost for large networks but is a more practical option since more people are using wireless technology)
49
What is a partial mech network topology?
Multiple routes exist between different devices
50
Advantage of a partial mesh network topology:
1) A compromise solution which lowers the amount of hardware needed compared to a full mesh network
51
Disadvantage of a partial mesh network topology:
1) Not all devices are fully connected
52
How do mesh network topologies work in general?
1) Decentralised, no need for a central switch/server 2) Mesh networks work by sending data along the fastest route from one device to another
53
Wireless networks: how do wireless networks work?
1) Uses radio waves to transmit data, more convenient than wired as you can move around (portable connection) while still being connected and cheaper as you used fewer wires (ideal as lots of cabling at home is undesirable)
54
Wireless networks: what is Wi-Fi and what is it used for?
1) A common standard for wireless networks 2) Can be used by multiple devices to connect to a LAN at the same time (handles large numbers of users)
55
Wireless networks: Advantages of Wi-Fi
1) Easier to set up and less expensive 2) Convenient (user can move around freely) 3) Connections have a range between 40 and 100 metres 4) Higher bandwidth than Bluetooth 5) Often used at home - routers, desktops, smartphones, etc.
56
Wireless networks: disadvantages of Wi-Fi
1) Slower speeds than wired networks 2) Relies on signal strength to the WAP 3) Signal can be obstructed 4) Less secure than wired networks
57
Wireless networks: what is Bluetooth and what is it used for?
1) Bluetooth is another, more modern standard for wireless networking 2) Usually a direct connection between two devices so that data can be shared
58
Wireless networks: advantages of Bluetooth
1) Ideal for connecting personal devices (e.g. wireless headphones/watches to a mobile phone or a wireless keyboard to a computer) 2) Lower power consumption than Wi-Fi
59
Wireless networks: disadvantages of Bluetooth
1) It has a short range (10 metres) 2) Lower bandwidth than Wi-Fi
60
Wired connections (ethernet): what is the ethernet?
A standard for networking technologies. Used for communicating on a wired LAN
61
Wired connections (ethernet): what does the ethernet include?
1) Includes a number of associated protocols (rules for governing communications) 2) Originally used in old style bus networks 3) Still used today in more modern star and mesh networks
62
Wired connections (ethernet): how is data transmitted?
Data is transmitted in frames which include: 1) preamble (introduction) bits used to synchronise transmission 2) start frame deliminator to signify the start of the data part of the frame 3) Source and destination MAC address 4) the actual data 5) error checking information
63
Advantages of wired connections:
1) Provides reliable, error free, fast communication between 2 points 2) Faster speeds than wireless 3) More secure than wireless
64
Disadvantages of wired connections:
1) User location is limited by the need for a physical cable connection 2) A set up relying on the Ethernet relies on lots of cables and hardware (harder to set up and more expensive)
65
How are wireless networks encrypted?
1) Wireless networks broadcast data, so must be encrypted to be secure 2) This is done by scrambling data into cipher text using a "master key" created from the SSID of the network and the password 3) Data is decrypted by the receiver using the same master key, so this key isn't transmitted (4) Protocols used for wireless encryption include WEP, WPA, WPA2 5) A handshaking protocol is used to ensure that the receiver has a valid master key before transmission to the device begins) (although wired networks are naturally more secure, encryption is still available and often a sensible precaution)
66
What is IP addressing?
*Communication between different networks uses IP addresses* 1) IP addressing is used to route packets on a WAN (used when sending data between TCP/IP networks e.g. over the Internet
67
What are the 2 versions of IP addresses?
IPv4 and IPv6
68
What is an IPv4 address?
32 bits in size, written as four numbers separated by periods (.), each number in the range 0-255 (e.g. 69.89.31.212)
69
What is an IPv6 address?
128 bits in size, written as eight groups separated by colons (:), each group is made up of four hex values representing 16 bits (e.g. 2001:85a3:0000:0000:8a2e:0370:7334)
70
What is MAC addressing?
*Communication on the same network uses MAC addresses* 1) MAC addressing is used to route frames on a LAN 2) Each MAC address is unique to every network interface card (NIC) 3) MAC addresses are assigned to all network-enabled devices and are mainly used by the Ethernet protocol on LANs. LAN switches read the MAC addresses and use them to direct data to the right device.
71
How does IP addressing work?
1) A router will have a unique WAN facing IP address and a LAN facing IP address 2) This enables a LAN device to have the same IP address as another device on another LAN 3) IPv4 is being replaced by IPv6 because unique static addresses are running out
72
What are MAC addresses?
MAC addresses are 48 or 64-bit binary numbers; to make them easier to use, they're converted into hexadecimal (e.g. 98-81-55-CD-F2-2F)
73
What do standards do?
Standards allow hardware/software to interact across different manufacturers/producers
74
What are standards?
Standards are a set of specifications for hardware/software. It makes it possible for manufacturers/producers to create products and services which are compatible with each other. Without standards, most devices wouldn't be able to interact or communicate.
75
Where do standards exist?
Standards exist in many areas of computer science, such as: - ASCII/UNICODE: character set standards - IEEE: standards for computer cables - HTML: standards for creating websites - document, image, and sound standards (e.g. PDF, PNG, MP3)
76
What are (communication) protocols?
A (communication) protocol is a set of rules for transferring data
77
What is a protocol?
A protocol is a set of rules that allows two (or more) devices to communicate. TCP/IP is the most important protocol which dictates how data is sent between networks.
78
What is TCP?
- Transmission Control Protocol - Communicate over LANs - Provides an error free transmission between two routers
79
What is IP?
- Internet Protocol - Communicate over WANs - Routes packets across a wide area network (WAN)
80
What is HTTP?
- Hypertext Transfer Protocol - Webpage requests - A client-server method of requesting and delivering HTML (hypertext makeup language) webpages
81
What is HTTPS?
- Hypertext Transfer Protocol Secure - Webpage requests - Encryption and authentication for requesting and delivering HTML webpages - Used when sensitive information needs to be transferred (e.g. passwords and bank account details)
82
What is FTP?
- File Transfer Protocol - File transfers - Used for sending files between computers, usually on a WAN
83
What is POP?
- Post Office Protocol - Email - Retrieves emails from a mail server - Removes it from server and transfers to your device
84
What is SMTP?
- Simple Mail Transfer Protocol - Email - Sends email to an email server
85
What is IMAP?
- Internet Message Access Protocol - Email - Used by mail clients to manage remote mail boxes and retrieve email from a mail server
86
What is a layer?
A layer is a group of protocols which have similar functions
87
What is the concept of layering?
1) The concept of layering is to divide the complex task of networking into smaller, simpler tasks that work with each other 2) The hardware and/or software for each layer has a defined responsibility 3) Each layer provides a service to the layer above it (data can only be passed between adjacent layers)
88
What do protocols in layer 4 cover?
- Turning data into websites and other applications and vice versa - HTTP, FTP, SMTP, HTTPS
89
What do protocols in layer 3 cover?
- Splitting data into packets and checking data is sent and delivered - TCP
90
What do protocols in layer 2 cover?
- Making connections between networks and directing data - IP
91
What do protocols in layer 1 cover?
- Passing data (as electrical signals) over the physical network - Ethernet
92
What are the advantages of layering?
1) Reduces the complexity of the problem into manageable sub-problems 2) As layers are self-contained, they can be changed without affecting other layers 3) Devices can be manufactured to operate at a particular layer 4) Products from different vendors will work together
93
Simplified version of the 4 layers:
4 - Browser using HTTPS 3 - TCP, error handling 2 - IP routing 1 - MAC frames sent over fibre optic (Media Access Control)

GCSE Computer Science (13 decks)

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