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computer science > 4.9 - Fundamentals of communication and networking > Flashcards

4.9 - Fundamentals of communication and networking Flashcards

1
Q

What is synchronous transmission?

A

In synchronous transmission, bits are transferred over a communication channel at a constant rate. The transmitter and receiver are synchronised by a common clock signal.

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2
Q

What is asynchronous transmission?

A

In asynchronous transmission, there is no common clock signal so start and stop bits are sent to control. The data is only sent when it is available as opposed to a constant rate.

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3
Q

What is serial transmission?

A

In serial transmission, bits are sent one after the other.

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4
Q

What is parallel transmission?

A

In parallel transmission, several bits can be sent at the same time using multiple cables, each with their own serial transmission. It does not require start and stop bits or synchronization signals like serial transmission, meaning it doesn’t use synchronous/asynchronous like serial. However it does use its own method of synchronous transmission.

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5
Q

What are the advantages of serial transmission?

A
  • Lower risk of interference, can be used over longer distances than parallel transmission, at a much higher frequency
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6
Q

What are the advantages of parallel transmission?

A
  • Transmits multiple bits simultaneously, making it faster than serial transmission
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7
Q

What is a bus topology?

A

A network topology where 1 cable called the backbone connects every device on the network

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8
Q

What is a terminator in a bus topology

A

A device that is placed at both ends of the backbone cable to absorb signals that reach the end of the cable and prevent them from reflecting back onto the network

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9
Q

What is collision in a bus topology?

A

When 2 or more devices transmit data at the same time, their signals collide and become garbled

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10
Q

What are the advantages of bus topology?

A
  • Simple to implement
  • requires less cabling than other topologies
  • cost-effective for small networks
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11
Q

What are the disadvantages of bus topology?

A
  • Susceptible to network congestion
  • Slower than other topologies as data must travel through all devices on the bus
  • Failure of the backbone cable can cause the entire network to fail
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12
Q

What is a star topology?

A

A type of topology where all devices are connected to a central hub or switch

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13
Q

What is bit rate?

A

The amount of bits that are being transmitted per second.

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14
Q

What is a hub in a star topology?

A

A central device that receives data and sends it to all connected devices

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15
Q

What is baud rate?

A

The amount of symbols being transmitted per second. A symbol is a change in signal (from 0-1 or 1-0).

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16
Q

What is bandwidth?

A

The amount of data that can be transmitted at the same time over a channel.

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17
Q

What is latency?

A

The delay from the time that a signal is sent, to the time that it is received, measured in milliseconds.

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18
Q

What is a switch in a star topology?

A

A central device that routes data to its destination based on the device’s address

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19
Q

What is a protocol.

A

A set of rules that determine the communication between devices

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20
Q

What are protocols used for?

A
  • The type of transmission (synchronous or asynchronous)
  • The types of interfaces (serial or parallel)
  • The transmission channel (wired or wireless)
  • The speed of transmission (bit rate or baud rate)
  • The error checking techniques
  • The format of the transmitted data
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21
Q

What are the advantages of a star topology?

A
  • Provides fast data transmission
  • Easy to add new devices to the network
  • Failure of single device does not affect the entire network
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22
Q

What is a thin-client?

A

A device that has limited main memory, limited secondary storage, and only basic processing capability. Thin clients are used when there is a powerful server that can be used to store most of the data and handle most of the calculations.

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23
Q

What are the disadvantages of star topology?

A
  • Requires more cabling than other topologies
  • can be expensive to implement for large networks
  • If the central hub or switch fails, the entire network can be affected
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24
Q

What are the advantages of a thin-client?

A
  • Cheaper to buy
  • Software is updated by the provider, and is often available at no cost
  • Can be more secure, as data is not held locally
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25
Q

What is network congestion?

A

When too many devices try to send data in a star topology through the central hub or switch, it causes the network to slow down

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26
Q

What are the disadvantages of parallel transmission?

A
  • Requires multiple wires, making it more difficult to implement
  • There can be crosstalk, which is when bits are transferred between wires due to the electrical current generated in transmission
  • There can be skew, which happens when bits arrive in the wrong order.
  • Limited range of up to 2m
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27
Q

What are the disadvantages of a thin-client?

A
  • They need to be connected to the internet
  • Requirement for a high bandwidth as more data is transferred between client and server
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28
Q

What are the disadvantages of serial transmission?

A
  • It has a lower rate of transmission because it transmits one bit at a time.
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29
Q

What is scalability in a network?

A

The ability of a network to expand and accommodate new devices as needed

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30
Q

What is a thick-client?

A

A device that has a large amount of memory and secondary storage and has a powerful processor. Thin clients are often used when graphical capabilities are needed such as for games or video editing.

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30
Q

What is a PAN

A

A personal area network - A term given to connected devices that are located within a few metres of each other

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31
Q

What are the advantages of a thick-client?

A
  • They don’t need to be connected to the internet to be functional
  • They don’t need a high bandwidth for their internet connection
  • Improved user experience as it has better graphics, sound and other multimedia features
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32
Q

What are the disadvantages of a thick-client?

A
  • They can be expensive to buy because of the powerful components
  • They can also be expensive to maintain
  • Limited scalability of the network as new clients are so expensive
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33
Q

What is a WAN

A

A wide area network - A network that connects two or more LANs over a large geographical area

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34
Q

What is a Client-Server network?

A

A type of computer network where devices are divided into two categories, clients and servers where clients request services or resources from servers.

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35
Q

What is a client in a client-server network?

A

a device that requests services or resources from networks

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36
Q

What is a server in a client-server network?

A

A device in a client-server network that provides services or resources to clients

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37
Q

What is the request-response model in a network?

A

The method of how clients and servers communicate in a client-server network. The client sends a request to the server, and the server sends a response back to the client.

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38
Q

What is JSON

A

JSON (JavaScript Object Notation) is a data interchange format based on a subset of JavaScript. It is built on two structures:
- A set of key-value pairs, where the key is a string and the value can be a string, number, Boolean, null, object, or array.
- An ordered list of values using arrays

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38
Q

What is XML

A

XML (Extensible Mark-up Language) is another data interchange format, and is an alternative to JSON. Like JSON it is used for storing and exchanging data on the web. It can contain a wide range of data formats and structures. It uses tags to define elements and attributes to define properties of those elements

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39
Q

What are the advantages of Client-Server networks?

A
  • Provides centralised control and security
  • allows for efficient management of resources and data
  • can handle large volumes of data
  • is highly scalable
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40
Q

What are the disadvantages of client-server networks?

A
  • Can be expensive to set up and maintain due to the need for powerful servers and dedicated IT staff
  • Dependence on servers can result in network downtime if servers fail
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41
Q

What are the advantages of JSON?

A
  • Easier for a human to read
  • More compact
  • Easier to create
  • Easier for computers to parse (analyse and break it down)
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42
Q

What is a peer-to-peer network?

A

A type of computer network where devices are connected to each other without a central server

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43
Q

What are the advantages of a peer-to-peer network?

A
  • Simple and inexpensive to set up and maintain
  • Does not rely on a central server, making it more resilient to network failures
44
Q

What are the disadvantages of JSON?

A
  • Lack of schema support (metadata that constrains the structure)
  • Can be vulnerable to security attacks such as injection attacks
  • Supports fewer data types than XML
45
Q

What are the disadvantages of peer-to-peer networks?

A
  • Can be less secure than client-server networks as there is no centralised control or security
  • Difficult to manage as the network grows
46
Q

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

A

The ability for devices to work together on a task or project, sharing resources and processing power

47
Q

What are the advantages of XML?

A
  • Allows a schema to be written
  • Widely supported by a variety of software tools, libraries, and programming languages
  • Platform-independent and can be used on any operating system, programming language, or device
48
Q

What are the disadvantages of XML?

A
  • Requires more storage space and bandwidth than other data formats
  • Parsing can be more complex and resource-intensive
  • Can be vulnerable to security attacks such as injection attacks
49
Q

What is CRUD?

A

CRUD is an acronym meaning Create, Read, Update, Delete. It is considered when making applications using persistent data, that all of these can be done,

50
Q

What is REST?

A

REST (Representational State Transfer) is an architecture style/standard for developing web services. It requires the use of distinct Hypertext Transfer Protocols for all four CRUD operations to create a standardised Client-Server interface. Once these standards are met, an application is considered RESTful.

51
Q

How does CRUD map to SQL and HTTP operations?

A

The CRUD operations can be mapped to HTTP like this, POST, GET, PUT, DELETE. They can also be mapped to SQL database operations like this, INSERT, SELECT, UPDATE, DELETE.

52
Q

Why can wireless signals be more easily intercepted than wired signals?

A

Because you don’t have to be physically connected to the network, you just need to be in range

53
Q

What is a wireless security protocol?

A

A method of securing a wireless network from unauthorised access or attacks

54
Q

What is a WEP?

A

Wired equivalent privacy - A wireless security protocol that uses a shared key to encrypt data transmitted over the network

55
Q

What are the weaknesses of WEP

A

WEP is easily cracked by attackers as it uses a weak encryption algorithm and the shared key can be easily intercepted

56
Q

What is the WebSocket protocol?

A

It is a protocol that uses TCP/IP. It provides bi-directional communication channel between a client and a server by establishing a HTTP handshake. Meaning both client and server can use the connection to start sending data at any time. It uses the same ports as HTTP and HTTPs (80 and 443), so it is treated as standard web traffic by the firewall.

57
Q

What are the advantages of the WebSocket protocol?

A

Data can be pushed from the server without having to be initiated by an HTTP request from the client. Every time an HTTP request is made, significant header data has to be transferred to the server which increases latency.

58
Q

What is an SSID?

A

A service set identifier - a unique name that identifies a wireless network

59
Q

What is an SSID broadcast?

A

The displaying of the wifi networks SSID to all devices in range

60
Q

What is a hidden SSID?

A

A wireless network that is configured to not broadcast its SSID. This means that in order for a device to connect to the network, it has to know the SSID in advance

61
Q

What are WebSocket frames?

A

They are similar to packets, but only used on a WebSocket connection. They consist of a header, which provides information about the frame type, length, and other control information, and a payload, which can be either text or binary data.

62
Q

What types of WebSocket frames are there?

A
  • Text frames
  • Binary frames, e.g. for image data
  • Ping-Pong frames, used to check the connection
  • Control frames, e.g. to close the connection
63
Q

What is network identification?

A

The process of identifying and verifying the identity of devices attempting to connect to a network

64
Q

What is a wireless network?

A

A computer network that allows devices to connect and communicate wirelessly over radio waves or other wireless communication technologies

65
Q

What is Bandwidth in a wireless network?

A

The maximum amount of data that can be transmitted over a network in a given time period

66
Q

What is a WAP?

A

A wireless access point - a device that enables wireless devices to connect to a wired network

67
Q

What is Wi-Fi?

A

A wireless networking technology that uses radio waves to allow devices to connect and communicate over a wireless network.

68
Q

What is network infrastructure?

A

The hardware, software and protocols that make up a computer network. This includes routers, switches, servers and network cables

69
Q

What is an open network?

A

A network that has been configured so that a password is not required

70
Q

Why are open networks not secure?

A

Because your data will not be encrypted

71
Q

How do subnet masks work?

A

A subnet mask specifies the number of bits allocated to the network ID and the host ID. On any subnet (subnetwork), the network ID for all hosts must be identical, and the host ID must be different.

72
Q

What is CSMA/CA?

A

Carrier-sense multiple access with collision avoidance - A protocol used in wireless networks to avoid collisions when multiple devices attempt to transmit data at the same time.

73
Q

How does CSMA/CA work?

A

1) listen to the channel to check for the presence of other signals. If there are no other signals, it will send the message, else it will try again a random time later
2) The receiver will send an acknowledgement message to verify the data has been received, else the sender will attempt to resend the message

74
Q

How do you calculate the amount of bits allocated to each part of the IP on a subnet mask?

A

Perform a logical bitwise AND operation on the subnet mask and the IP address to find out how much of the IP is dedicated to the network ID.

75
Q

What types of IP formats are there?

A

There is the previous standard IPV4 with 32 bits, and IPV6 with 128 bits.

76
Q

Why was IPV6 introduced?

A

It was introduced because all the IPv4 addresses were used up, because there are only 4 billion available.

77
Q

What is the main problem with CSMA

A

The hidden node problem - When a sending device checks if the channel is idle, it can only check within its broadcast range. However, a device can be out of range from the broadcast from another device, but still be on the network connecting them, so they could both be sending data to the WAP at the same time.

78
Q

What is RTS/CTS?

A

Request to send/clear to send - an optional method that works with CSMA/CA which solves the hidden node problem. It works by sending an RTS (request to send) when it determines that a channel is idle, and waits for a CTS (clear to send) reply before sending. This ensures that there will be no collisions with data being sent to the WAP.

79
Q

What is a NIC?

A

A network interface card - A hardware component that connects a device to a computer network. This allows it to communicate with other devices on the network

80
Q

What is a WNIC

A

A wireless network interface card - A type of network interface card that allows devices to connect to wireless networks using radio waves.

81
Q

What is a MAC address?

A

A unique identifier assigned to a network interface card which is used to identify the device on a network

82
Q

What is a switch?

A

Used in a network to connect devices together, allows communication between devices such as a printer or multiple computers.

83
Q

What is a MoDem?

A

Modulates and demodulates data - converts signals from analogue to digital and back again.

84
Q

What does TCP/IP stand for?

A

Transfer control protocol/internet protocol.

85
Q

What are the layers in TCP/IP?

A

Application, Transport, Network, Link.

86
Q

What is the functions of the application layer in the TCP/IP stack?

A

Application layer applies protocols depending on the application, such as an email application may use IMAP or POP3.

87
Q

What is the function of the transport layer in the TCP/IP stack?

A

The transport layer defines the transport protocol such as FTP, it also splits the data into packets (all packet switching functions, number of packets, packet number etc.) and defines the port number. Also creates a connection to check if the data is received.

88
Q

What is the function of the network layer in the TCP/IP stack?

A

Applies the IP addresses for the sender and receiver.

89
Q

What is the function of the link layer in the TCP/IP stack?

A

The link layer defines the physical components, such as if it is travelling over ethernet, adds information about the mac address for the sender and the specific Network Interface Card.

90
Q

What is a private IP address/non routable adress?

A

Networks use subnet masking to define which part of the IP is the Host and which part is the network, the host is a client and uses private IP for added security and because there are not enough IP addresses for every computer to have a public. And the Network has a public IP such as the router. This address is used when routing packets and is applied on the network layer.

91
Q

What are the advantages of JSON over XML?

A

JSON is more compact and easy to understand.

92
Q

What defines a thin client netwrok?

A

Central server does all the processing, inputs from devices, OS installed on server, applications installed on server. Needs higher bandwidth for devices, needs to use a switch instead of a hub, slower processors on thin clients.

93
Q

What protocol is port 20?

A

File Transfer Protocol (FTP) DATA

94
Q

What protocol is port 21?

A

File Transfer Protocol (FTP) CONTROL

95
Q

What protocol is port 22?

A

Secure Shell (SSH) Remote login

96
Q

What protocol is port 23?

A

Telnet (unencrypted) Remote login

97
Q

What protocol is port 25?

A

Simple Mail Transfer Protocol (SMTP)

98
Q

What protocol are ports 80 and 8080?

A

HyperText Transfer Protocol (HTTP)

99
Q

What protocol is port 110?

A

Post Office Protocol v3 (POP3)

100
Q

What protocol is port 143?

A

Internet Mail Access Protocol (IMAP)

101
Q

What protocol is port 443?

A

HyperText Transfer Protocol Secure (HTTPS)

102
Q

Why is Javascript interpreted not compiled?

A

Compilers are specific to processors and the website wouldn’t know what type to use. There are no Javascript compilers.

103
Q

What does DHCP do?

A

Automatically assigns private IP addresses to devices on a network.

104
Q

What are the stages in DHCP?

A

DORA
Discovery - Device sends a discover message to the DHCP server.
Offer - The DHCP server sends an offer to the device, which contains the IP address that is offered, the subnet mask, the lease duration, and the IP address of the DHCP server making the offer.
Request - Client broadcasts a request to the IP of the DHCP server.
Accept - Once the DHCP server retrieves the request, it has accepted the IP configuration.

105
Q

How does a firewall protect a network?

A

Block traffic from specific IPs. Block types of packets. Acts as a proxy server so all traffic passes through it. Allows only relevant packets to pass through.

106
Q

What are the advantages?

A

Avoids errors such as duplicating IP addresses. Reduces time for configuring host. Reduces need for expert knowledge.

107
Q

What is the SSH protocol used for?

A

Used for secure remote access for server engineers. Used for management.

108
Q

What is port forwarding?

A

Allows remote to connect to a specific computer, or service within a private local area network.

109
Q

What is a gateway?

A

Device that allows data to flow from one network to another. When two networks use different protocols a gateway is used to convert packets to conform to both protocols.

110
Q

What is NAT?

A

Process of mapping private IP to public IP by modifying the address information.

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