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IGCSE CIE Computer Science > 2 Data Transmission > Flashcards

2 Data Transmission Flashcards

1
Q

How is data transmitted?

A

It is broken down into very small units called packets.

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2
Q

Can you describe the structure of a data packet?

A

Packet Header
Paylod
Trailer

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3
Q

What does the payload contain?

A

Contains the actual data from the file that you are sending.

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4
Q

What does the trailer contain?

A
  • Marker to indicate end of packet
  • Data for any error detection systems
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5
Q

Can you describe the process of packet switching?

A
  • Data is broken down into packets
  • Each packet is individually sent from one device to another
  • Each data packet could take a different route.
  • A router controls the route a packet takes.
  • Packets may arrive out of order
  • After all packets arrive, packets are reorderd.
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6
Q

What is serial data transmission?

A

Data is sent one bit at a time down a single wire.

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7
Q

What is parallel data transmission?

A

Data is sent multiple bits at a time down multiple wires.

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8
Q

What is simplex tranmission?

A

data is transmitted in a single direction only

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9
Q

What is half duplex transmission?

A

data is transmitted in both directions, but only one direction at a time.

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10
Q

What is full-duplex transmission?

A

data is transmitted in both directions at the same time.

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11
Q

What are the advantages of serial data tranmission?

A
  • Less chance of data being skewed as it is sent one bit at a time.
  • As data is sent along 1 wire, there are less chances of interference, therefore less chances of error in data
  • only 1 wire is need, therefore it is cheaper to buy and cheaper to manufacteur.
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12
Q

What is a USB and how does it work to transmit data?

A

Universal Serial Bus is an industry standard that is used to transmit data.

A USB connection uses serial data transmission to transmit data between the devices. However it is a special type of serial data transmission connection that is designed to transmit data at high speeds.

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13
Q

What are the advantages of the USB interface?

A
  • simple interface. The USB cable to device can only fit into the USB one way. Therefore means less errors in connecting devices are likely to be made.
  • The speed of a USB connection is relatively high, so data transfer is quick
  • USB interface is a universal standard so a USB port is included in many different devices.
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14
Q

What are the disadvantages of the USB interface?

A
  • The length of the USB cable is limited, normally to 5 metres.
  • Tranmission speed is relatively high but slower than other types of connection such as ethernet.
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15
Q

What are the methods of error detection for detecting errors in data after transmission?

A
  • Parity check
  • checksum
  • echocheck
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16
Q

What is a parity check?

A
  • type of error detection method that adds an additional bit to each byte to create an odd or even sum.
17
Q

What is a checksum?

A

Type of error detection method. A checksum uses a calculated value to check for errors. A value is calculated from the data that will be transmitted, before transmission takes place. Checksum values are compared after transmission to see if they match.

18
Q

What is echo check?

A

A type of error detection method that sends a copy of the transmitted data back to the sender to be compared with the original data sent.

19
Q

What is a check digit?

A

A type of error detection method that is used for data entry. A calculation is performed on the data entered to create a value. Check digits values are compared to see if data entered is correct.

20
Q

What are some examples of when a check digit is used?

A
  • ISBN (international standard book numbers)
  • bar codes
21
Q

What is automatic repeat query (ARQ)?

A

A type of error detection method that uses acknowledgement and timeout to see if data has arrived correctly after transmission.

22
Q

What is acknowledgement?

A

A message that is sent from one device to another to indicate whether data is recieved correctly.

23
Q

What is a timeout?

A

A period of time that is set and used to wait for an acknowledegment to be recieved.

24
Q

What is encription?

A

a method of securing data for storage or transmission that scrambles it and makes it meaningless.

25
Q

What is plain text?

A

the name given to data before encryption.

26
Q

What is cipher text?

A

the name given to data after encryption.

27
Q

What is an encyrption key?

A

A type of algorithm that is used to encrypt data.

28
Q

What is symmetric encryption?

A

A type of encryption that uses the same key to encrypt and decrypt data.

29
Q

What is asymmetric encryption?

A

a type of encryption that uses two different keys to encrypt and decrypt the data.

IGCSE CIE Computer Science (3 decks)

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