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A level Computer Science > Unit 6 - Communication > Flashcards

Unit 6 - Communication Flashcards

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1
Q

What is serial transmission?

A

Serial transmission is a type of transmission involving one bit being transmitted at a time across a singular channel/line. Sometimes two lines are required for two-way communication.

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2
Q

What is parallel transmission?

A

Parallel transmission is a form of transmission involving several bits being transmitted simultaneously across multiple wires/lines, connected to internal components.

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3
Q

Give an example of serial transmission.

A

An example of serial transmission is a USB (Universal Serial Bus).

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4
Q

Describe the appearance of parallel transmission.

A

Parallel transmission involves a ribbon consisting of several wires attached together. Depending on the bits of the block of data, the same number is used for the number of channels.

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5
Q

Give a disadvantage of serial transmission.

A

Compared to parallel transmission, because serial transmission only uses one line generally, it performs slower transmission of data.

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6
Q

Give a disadvantage of parallel transmission.

A

Skew - Parallel transmission uses several lines/channels with bits being transmitted simultaneously. Because of this, bits on differing channels may travel at different speeds.

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7
Q

Describe a disadvantage of parallel transmission.

A

Crosstalk - Due to electromagnetic interference across lines, this may cause line interference as the frequency (speed of transmission) increases. This may result in corruption of data.

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8
Q

Explain the distance parallel transmission can travel at.

A

Although it can travel faster than serial transmission, because parallel transmission suffers from problems such as skew or crosstalk, this makes it less reliable. Therefore, it can only travel short distances up to 2 metres.

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9
Q

Explain the distance serial transmission can travel at.

A

Serial transmission is a slow method yet it doesn’t have any major issues affecting it unlike parallel transmission. This makes it more reliable to travel longer distances.

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10
Q

Give an advantage of serial transmission.

A

When producing serial connectors for serial transmission, the small size and small complexity means production costs are cheaper. This means devices which use these connectors are durable and have good performance despite being cheaper.

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11
Q

What is synchronous transmission?

A

Synchronous transmission is where long streams or blocks of data are sent at regular intervals, and during this transmission they are timed via a clock signal.

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12
Q

What is asynchronous transmission?

A

Asynchronous transmission is where a byte of data is transmitted, consisting of a start bit preceding the byte and a stop bit following the byte. A parity bit is added to the byte as the 8th bit for error detection.

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13
Q

Give a use of asynchronous transmission.

A

Asynchronous transmission is a very slow method of serial transmission due to the transmission of large amounts of bits. This makes it well suited for low speed connections such as a mouse or keyboard.

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14
Q

What is latency?

A

Latency is the time delay between sending the first packet of communication and receiving the packet at the destination.

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15
Q

What is protocol?

A

The protocol is the set of rules relating to communication between devices.

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16
Q

Give examples of protocol rules.

A
  • Deciding whether to use asynchronous or synchronous transmission
  • Data format
  • Odd or even parity checking procedures
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17
Q

What is the bit rate?

A

The bit rate is the number of bits (1s and 0s) transmitted per second in a wired or wireless data link.

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18
Q

Define baud rate.

A

The baud rate is the rate at which the signal in a communications channel changes state. It is measured in Mbit/s.

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19
Q

Give the bit rate formula.

A

Bit rate = Baud rate x number of bits per signal

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20
Q

What is bandwidth?

A

Bandwidth is a measure of the maximum capacity of the communications channel. Units are bits per second, Mbps or Gbps

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21
Q

What is baseband?

A

Baseband is a signal involving one bit being carried at a time, and at each signal change, one bit is transmitted.

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22
Q

What is broadband?

A

Broadband is a signal involving multiple bits being carried so at each signal change 2 bits are transmitted.

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23
Q

Define LAN.

A

LAN (Local Area Network) is a network involving 2 or more computers connected together in a small geographical region. They are typically confined to one building or site.

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24
Q

What is a network topology?

A

This is an arrangement of all computing devices/nodes in a network.

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25
Q

Describe the bus topology.

A

The bus network topology is a type of network topology where the nodes/computing devices are connected in a daisy-like structure in a singular central communications channel. All nodes are connected to a singular backbone cable, which also connects to a terminator, preventing data bouncing back.

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26
Q

What is used in a bus topology to ensure data is transmitted in one direction?

A

CSMA/CD (Carrier Sense Multiple Access) technology enables nodes to transmit data in one direction, and helps avoid data collisions.

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27
Q

Give an advantage of the bus topology.

A

The bus topology network is relatively cheap/inexpensive to set up.

28
Q

Give another advantage of the bus topology.

A

Devices can be easily added.

29
Q

Give a disadvantage of the bus topology.

A

There is poor security.

30
Q

Give another disadvantage of the bus topology.

A

Cable length is limited.

31
Q

Describe a third disadvantage of the bus topology.

A

In heavy use, performance can severely weaken; this may be due to data collisions.

32
Q

Describe the star topology.

A

The star network topology is where there is a central hub/node acts as a central connection point, providing connection to all other nodes in the network.

33
Q

Define the switch in a star topology network.

A

The switch is a component which message/communication for a specific node it is intended for. It also holds the MAC addresses for all devices connected to it.

34
Q

Define the hub in a star topology network.

A

The hub is a component of a star topology which broadcasts the message to all computing devices on the LAN.

35
Q

Give an advantage of the star topology network.

A

The star topology network performs relatively good.

36
Q

Describe another advantage of the star topology network.

A

If a switch is used then more security and privacy is encouraged due to the message only being sent to the intended recipient.

37
Q

Give a disadvantage of the star topology.

A

Unlike the bus topology, the star topology network is quite expensive to set up due to the several cables required.

38
Q

Give another disadvantage of the star topology.

A

The central device is a point of failure; if the central device stops working, then the nodes which heavily rely on it won’t know what to do so they’ll stop working as well.

39
Q

Define physical topology.

A

The physical topology is focused on how the devices are physically connected to each other; are they connected in a bus or star topology structure, cable length…

40
Q

What is the logical topology of a network?

A

The logical topology is focused on how the devices actually communicate across the physical structure; e.g. some nodes arranged in a star topology may communicate in a bus network.

41
Q

What is in every networked device?

A

Each and every networked device contains an NIC (Network Interface Card), and the NICs all have a unique MAC (Media Access Control) address hardcoded during manufacture.

42
Q

Give the two types of server architecture.

A
  • Client-server network

- Peer-to-peer network

43
Q

What is a server?

A

A server is a powerful computer which provides several services and resources for the client.

44
Q

What is a client?

A

A client is a computer which requests services/resources from the centralized server.

45
Q

Give an outline of the client server network.

A

The client requests a service or resource from the server by sending a query. The server sends the query to another server, and then it will send a response to the client.

46
Q

Give features of a client-server network.

A
  • The centralized server manages security of the network
  • The central server performs some processing tasks
  • Client-server network typically works with all kinds of organisation of files; large or small.
47
Q

What kinds of requests will clients give to servers?

A
  • Printing a document
  • Emailing
  • Backing up files
  • File storage…
48
Q

Give examples of specialized servers that are found in a client-server network.

A
  • File server
  • Mail server
  • Database server
  • Print server
49
Q

Give features of a peer-to-peer network.

A
  • There is no centralized server to control files or security.
  • All files can be easily seen through other computers.
  • All computers can easily communicate with each other
50
Q

Give a use of peer-to-peer networks.

A

P2P networks are widely used in WANs (Wide Area Networks) such as the internet, where they are sometimes used to illegally distribute copyrighted material such as films. This is done as the data is transmitted from computer to computer rather than directly from the server.

51
Q

Give a problem with peer-to-peer networking.

A

Peer-to-peer networking can be used for piracy of films or music, and this has been very controversial; e.g. leaking unreleased music.

52
Q

What is cloud computing?

A

Cloud computing is a metaphorical/imaginative term referring to internet networking with the use of remote servers from big software companies such as Microsoft, Apple, Dropbox…

53
Q

Give a benefit of cloud computing.

A

All your data and files are automatically backed up to the cloud so there is no danger of losing.

54
Q

Give another advantage of cloud computing.

A

Software and files/data don’t need to be unnecessarily downloaded as they are held by the software manufacturer in the cloud.

55
Q

What is Wi-Fi?

A

Wi-Fi is wireless networking technology used to provide wireless internet connections with high-speed. Each wireless network has a Wireless Access Point (WAP).

56
Q

Give examples of Wi-Fi hotspots.

A

Wi-Fi hotspots are found in cafes, libraries, hotels or other public areas.

57
Q

What is needed for connecting to a wireless network?

A
  • ISP (Internet Service Provider)
  • Modem and wireless router (often combined)
  • Network Interface Card/Controller (NIC)
58
Q

What does the wireless access point require?

A

The WAP requires connection to a router, and the router requires connection to the modem.

59
Q

What is an SSID?

A

An SSID (Service Set IDentifier), is an ID used to identify the names of wireless networks. All devices on a network must use the SSID, though the SSID can be hidden as this makes it harder to detect by possible cyber attackers.

60
Q

Give a risk of using a wireless network.

A

Compared to wired networks, wireless networks are less secure as there is a risk of unauthorized access by possible cyber attackers and any transmitted data could be intercepted.

61
Q

Give security methods to keep a wireless network secure.

A
  • WPA
  • WPA2
  • MAC address whitelists.
62
Q

What will happen if two devices attempt to transmit at once?

A

If two devices try transmitting over a singular wireless access point, then this can create some trouble so to prevent this issue, a protocol is used to lay out rules for communication between devices.

63
Q

What is CSMA/CA?

A

CSMA/CA (Carrier Access with Multiple Access/Collision Avoidance), is a type of protocol used to prevent data collisions, where a station can only transmit data when the channel is idle.

64
Q

Describe the hidden node problem.

A

The hidden node problem is a situation where there is a WAP, surrounded by two nodes. The node can see the WAP but can’t directly communicate with the other node.

65
Q

Explain the RTS/CTS protocol.

A

The RTS/CTS protocol is a protocol which helps stations request to send data and clear to transmit data across an idle channel. In a flow chart, if the channel is idle then the station will send an RTS (request to send) signal and then check whether a CTS (clear to send) signal is received.

A level Computer Science (12 decks)

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