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A Level Computer Studies > Unit 6 - Communications and Networks > Flashcards

Unit 6 - Communications and Networks Flashcards

1
Q

What are the two types of cables?

A

Serial and parallel

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2
Q

What are the advantages of serial cables?

A
  1. Reliable over long distance
  2. Reliable with high frequencies
  3. Smaller connectors
  4. Cheaper as fewer wires are needed
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3
Q

What is skew?

A

Data on different cables within a parallel wire moving at different speeds so that they arrive at their destination at different times, this causes latency and data can be lost

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4
Q

What is crosstalk?

A

Electromagnetic interference between two cables within a parallel wire causing data to be lost or corrupted meaning it has to be resent

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5
Q

What happens to crosstalk as the frequency is increased?

A

Becomes more pronounced

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6
Q

What are the disadvantages of serial transmission?

A
  1. Two cables have to be added for two way transmission
  2. Slow as data has to be sent one after the other
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7
Q

What are the two types of data transmission?

A

Synchronous and asynchronous

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8
Q

Define latency

A

The time delay that occurs when transmitting data between devices

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9
Q

What is synchronous transmission?

A

Data is transmitted where the pulse of the clock of the receiving device and the sending devices are in times with one another

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10
Q

What is asynchronous transmission?

A

Data is transmitted between two devices that do not share a common clock signal

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11
Q

Compare synchronous and asynchronous transmission

A

Synchronous transmission is quicker and more efficient as asynchronous transmission requires additional bits to be sent which means sending more data and there are gaps between transmission. However, asynchronous transmission is cheaper so it is often used in low speed connections such as between a mouse or a keyboard.

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12
Q

Why are protocols necessary?

A

All devices involved in communications must agree on the rules of information transfer

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13
Q

What points do protocols cover?

A
  1. Standards for physical connection such as cabling
  2. The rate of transmission
  3. Data format
  4. Whether the transmission is synchronous or asynchronous
  5. Error checking procedures (even or odd parity)
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14
Q

What is bit rate?

A

The number of bits transmitted in one second over a wired or wireless data link

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15
Q

What is baud rate?

A

The rate at which the signal in a communications channel changes state

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16
Q

What equation links bit rate and baud rate?

A

Bit rate = baud rate x number of bits per signal

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17
Q

Why can’t the baud rate ever be higher than the bit rate?

A

The baud rate is a measure of how many times the signal changes state and the maximum number of times is once for every transition between two bits

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18
Q

What is the difference between baseband and broadband?

A

Baseband carries one signal at a time, a bit is represented by high or low voltage in the cable.
Broadband carries multiple signals on a fixed carrier wave which means that bits are sent as variations on the wave.

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19
Q

What is broadband?

A

A measure of the maximum capacity of a communications channel

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20
Q

What is a LAN?

A

Two or more computers connected together within a small geographic location .e.g. home or office

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21
Q

What is a standalone?

A

A computer which is not connected to any other computing device

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22
Q

What is a WAN?

A

Two or more computers connected together and the connection spans a large area .e.g. international

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23
Q

What is a bus topology?

A

An arrangement where nodes are connected in a daisy chain by a single central communications channel

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24
Q

What is a star topology?

A

An arrangement where a central switch or hub provides a common connection point for all other nodes and each node has a connection directly to the central hub or switch

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25
Q

What does it mean if nodes are passive?

A

They do not actively communicate with one another

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26
Q

What happens if two nodes try to transmit at the same time in a bus topology?

A

CSMA/CA will detect this and halt the transmission from both nodes, each nodes will then have to wait a random amount of time before it can try to transmit again

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27
Q

What are the advantages of a bus topology?

A
  1. Cheaper to install than a star topology
  2. Easier to install than a star topology
  3. Easy to add new client
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28
Q

What are the disadvantages of a bus topology?

A
  1. Not good for large networks
  2. Low security
  3. Adding users to the network increases latency
  4. The main cable failing will affect all the users
  5. Less reliable than a star network
  6. More difficult to find faults
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29
Q

What does CSMA/CD stand for and what does it do?

A

Carrier Sense Multiple Access and Collision Detection. This is a type of software that can be used in wired networks to detect possible collisions and manage transmissions.

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30
Q

What type of software is often used in wireless networks?

A

CSMA

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31
Q

How does the switch in a star topology send messages to the right device?

A

Each device contains a Network Interface Card (NIC) and each one of these is encoded with a Media Access Control (MAC) address. The switch will have the MAC address for every device and can cross reference it with the message being sent. It can then send the message to the right computer.

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32
Q

What is the difference between a hub and a switch?

A

A switch will send messages to individual devices within a star topology where as a hub will broadcast the message to every device within the topology

33
Q

What are the advantages of a star topology?

A
  1. Fast connection as each client has a dedicated cable
  2. Will not experience the same latency as other topologies when there are many users connected
  3. It is easier to trace faults
  4. Each client-server connection is unique so it is relatively secure
  5. It is easy to add new clients
  6. A cable failure only affects one client
34
Q

What are the disadvantages of a star topology?

A
  1. Expensive due to extra cables
  2. A client may not be able to receive data if its cable fails
  3. Can be difficult to install
  4. The server can become congested
  5. The whole network fails if there is a problem with the central server
35
Q

What is a physical topology?

A

How the devices in a network are physically connected

36
Q

What is a logical topology?

A

The conceptual way data is transmitted around the network and which protocols are used for communications

37
Q

List the features of a client-server network

A
  1. A central server to manage security
  2. Files held on central server
  3. Processing tasks performed by central server
  4. Client issue request to the server for services
  5. Suitable for many different types of organisation
  6. May require staff to administer it
38
Q

List the features of a peer-peer network

A
  1. No central server or security
  2. Suitable for small companies with fewer computers
  3. All computers can easily access file on others
  4. All computers communicate directly with one another
  5. Once a computer is switched off, data cannot be retrieved
39
Q

Define client

A

A device which requests services from another device

40
Q

Define server

A

A device which provides services to other devices

41
Q

Describe the process the server takes to provide services to another device

A

The server waits for a request, acts upon the request by carrying out the necessary processes and then returns the result of these processes to the client

42
Q

What will happen if a server is unable to perform the processes needed to complete a request?

A

It will send the request to another server or device to carry out the processes in which case the original server becomes a client

43
Q

What is cloud computing?

A

This is a form of computing which employs the use of the internet to store and share files or software which means that it does not have to sit on the user’s hard drive

44
Q

What are the advantages of cloud computing?

A
  1. Does not require any additional software to be downloaded
  2. Software and data is accessible from any computer
  3. Software and data are automatically backed up
  4. Software and data do not take up space on the user’s hard drive
45
Q

What are the disadvantages of cloud computing?

A
  1. If the internet goes down then the cloud goes down too and nothing is accessible
  2. The cloud is not secure and can be easily hacked
  3. The ownership of data is unclear once it is uploaded to the cloud
  4. Little to no customer support
  5. The cloud management may require their formats and applications to be used
  6. Can lead to quickly escalating costs as you have to progressively pay for more features
46
Q

Define Wi-Fi

A

A wireless networking technology that provides high-speed internet and network connections

47
Q

What is a WAP?

A

Wireless Access Point

48
Q

What does a WAP allow you to do?

A

Access the internet

49
Q

What are the advantages of Wi-Fi?

A
  1. Access from anywhere
  2. Easier to set up and inexpensive
  3. Convenient
  4. Can handle a large number of users
  5. Easy information and data transfer (social media)
50
Q

What are the disadvantages of Wi-Fi?

A
  1. Slower than a wired network
  2. Relies on signal from WAP
  3. Signals can be easily obstructed
  4. Less secure
51
Q

What is a wireless network interface card?

A

A device component that allows it to establish a connection with the nearest WAP

52
Q

What hardware is required for a wireless network connection (in order)?

A
  1. Wireless network interface card
  2. Wireless access point
  3. Router
  4. Modem
53
Q

Define SSID

A

A service set identifier which allows a user to connect to the network

54
Q

Why are SSID’s useful?

A

They can be hidden which means that no one can access the network unless they know it, you can add a password or/and change the name yourself

55
Q

What is a MAC whitelist?

A

A list that is held by network that details which MAC addresses are allowed to connect to that network

56
Q

What is the purpose of the start bit in asynchronous transmission?

A

The start bit is sent so that the receiving device can prepare for incoming data

57
Q

What is the purpose of the stop bit in asynchronous transmission?

A

The stop bit is sent to the signal the end of the transmission so that the receiver can process the data accordingly

58
Q

How are bit rate and bandwidth related?

A

They are directly proportional

59
Q

Define a firewall

A

Hardware or software that monitors ingoing and outgoing traffic to a network and prevents unauthorised access through the use of packet filtering or stateful inspection

60
Q

Define packet filtering

A

Checking packet headers against a list of rules (packet filters) to determine whether or not the packet is allowed through .e.g. the packet filter could include an IP address that is blocked from sending packets to the network

61
Q

Define stateful inspection

A

Continuously monitoring incoming and outgoing traffic after a connection is established by analysing the packet types and checking the payloads

62
Q

Define proxy server

A

Provides anonymity to client devices by sitting between the client and the firewall

63
Q

How does a proxy server provide anonymity to clients?

A

The packets that have passed through the firewall will all be passed to the proxy server and the proxy server will then pass the information to the client, this means that the proxy server is the only server that knows which client has made which request

64
Q

Define serial transmission

A

Data is transmitted one bit at a time down a single wire

65
Q

Define parallel transmission

A

Data is transmitted several bits at a time down multiple wires

66
Q

What are the disadvantages of parallel transmission?

A
  1. Crosstalk
  2. Skew
  3. Signal degradation as speed or distance increases
67
Q

Define bandwidth

A

A measure of the capacity of the channel data is being sent down

68
Q

What is the relationship between time and bandwidth?

A

Bandwidth increases over time meaning the bandwidth available to the user increases each year

69
Q

How is bandwidth related to carrier wave frequencies?

A

Bandwidth is another way of expressing the range of frequencies available on a carrier wave

70
Q

What is the baud rate determined by?

A

The transmission medium

71
Q

What are the three types of latency when transmitting data?

A

Propagation latency, transmission latency and processing latency

72
Q

What is propagation latency?

A

The amount of time it takes for a logic gate within a circuit to transmit the data

73
Q

What is transmission latency?

A

The amount of time it takes to pass through a communication medium (a wire)

74
Q

What is processing latency?

A

The amount of time it takes data to pass around a network which is dependent on the number of servers and devices it has to pass through

75
Q

What happens if two devices are using synchronous transmission and their transmission rates are not in synch with one another?

A

Data can be lost

76
Q

Define protocols

A

A set of rules

77
Q

What is a NIC?

A

A card that enables a devices to connect to a network

78
Q

What is a network topology?

A

The layout of a network usually in terms of its conceptual layout rather than physical layout

79
Q

State four methods of securing a wireless network

A
  1. Changing the SSID from the default value and hiding it
  2. Ensuring that all devices connected to the network are WPA/WPA2 compliant
  3. Use a string encryption
  4. Utilise a MAC whitelist

A Level Computer Studies (15 decks)

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