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.Computer Science > Chapter 2 - Data transmission > Flashcards

Chapter 2 - Data transmission Flashcards

(46 cards)

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1
Q

What are packets?

A

Small units of data.

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2
Q

What are the three different sections that each packet of data contains?

A
  1. Packet header
  2. Payload
  3. Trailer
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3
Q

What is a packet header?

A

A section of a packet that contains information about the contents of the packet and its destination.

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4
Q

What information does the packet header contain?

A
  1. Destination address
  2. Packet number
  3. Originators address
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5
Q

What is an internet protocol (IP) address?

A

The unique address that is given to a device when it is connected to a network.

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6
Q

What is the payload?

A

The actual data that the user is sending to the receiver.

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7
Q

What is the trailer?

A

A section of a packet of data that contains information about any error checking methods that may be used.

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8
Q

What is packet switching?

A

A method of transmitting data packets across a network. Each data packet is able to take an individual pathway across the network.

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9
Q

What is a network?

A

Computers and devices that are joined together using cables or wireless technology.

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10
Q

What is a router?

A

A network component that examines a data packet to obtain its destination address and then forwards the packet to this address.

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11
Q

What are the different methods of data transmission?

A
  • Serial
  • Parallel
  • Simplex
  • Half-duplex
  • Full-duplex
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12
Q

What is serial data transmission?

A

A transmission method where data is sent one bit at a time down a single wire.

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13
Q

What is parallel data transmission?

A

A transmission method where data is sent multiple bits at a time down multiple wires.

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14
Q

What are the advantages and disadvantages of serial data transmission?

A

Advantages:
- As data is sent one bit at a time, it arrives in order. This means less chance of data being skewed.
- As data is sent along a single wire, there is less chance of interference so less chance of errors.
- Only one wire is needed so it is cheaper to manufacture and buy.

Disadvantages:
- As data is sent one bit at a time, transmission of data is slower
- Additional data may need to be sent to indicate to the receiving device when the data transmission has started and stopped (start bit and stop bit)

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15
Q

What are the advantages and disadvantages of parallel data transmission?

A

Advantages:
- As data is sent multiple bits at a time, data transmission is quicker
- Many devices use parallel data transmission to transmit data internally so there is no requirement to convert this to serial data transmission to transmit data across a network

Disadvantages:
- As data is sent multiple bits at a time, bits do not arrive in order and need to be reordered after transmission which increases risk of data being skewed
- As data is sent along multiple wires, there is more chance of interference so higher chance of errors
- Multiple wires are needed so it is more expensive to manufacture and buy

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16
Q

In which situations is serial data transmission and parallel data transmission more suitable?

A

Serial data has less chance of being skewed and less chance of interference so it is more suitable over long distances.

Parallel data has more chance of being skewed and more chance of interference so it is more suitable over short distances (limited to approximately 5 metres).

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17
Q

What is a simplex transmission?

A

A transmission method where data is transmitted in a single direction only.

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18
Q

What is a half-duplex transmission?

A

A transmission method where data is transmitted in both directions, but only one direction at a time.

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19
Q

What is a full-duplex transmission?

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A

A transmission method where data is transmitted in both directions at the same time.

20
Q

What is USB?

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A

An industry standard that is used to transmit data.

21
Q

What is a USB port?

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A

A socket that is part of a device or computer that enables you to insert a USB cable.

22
Q

What is a USB cable?

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A

A type of transmission media that uses the USB method to transmit data.

23
Q

What is a USB connection?

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A

A collective name for using a USB cable plugged into a USB port to transfer data from one device to another.

24
Q

What is a USB device?

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A

The name of a device that plugs into a USB port on a computer.

25
What are the advantages and disadvantages of the USB interface?
Advantages: - Simple interface and can only fit into the USB one way so there are less errors in connecting devices - Speed of a USB connection is high so data can be transferred quickly - USB interface is a universal standard for connecting devices so is included in many different devices - When a USB device is inserted into a port it is automatically detected and will only need to download the drivers to operate the hardware that has been connected once - A USB connection can be used to power or charge a device Disadvantages: - Length of a USB cable is limited, normally to 5 metres - Transmission speed isn't as high as other types of connection such as ethernet
26
What is ethernet?
Another type of connection that can be used to transmit data within a network.
27
What are the 5 error detection methods?
- Parity check - Checksum - Echo check - Automatic repeat request (ARQ) - Check digit
28
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.
29
What is a checksum?
A type of error detection method that performs a calculation on the data to create a checksum value. Checksum values are compared after transmission to see if they match.
30
What is an echo check?
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.
31
What is an automatic repeat request (ARQ)?
A type of error detection method that uses acknowledgement and timeout to see if data has arrived correctly during transmission.
32
What is an acknowledgement?
A message that is sent from one device to another to indicate whether data is received correctly.
33
What is a timeout?
A period of time that is set and used to wait for an acknowledgement to be received.
34
What is the process of the positive acknowledgement method?
1. Sending device transmits the first data packet 2. Receiving device receives the data and checks it for errors 3. Once the receiving device knows it has received the data error-free, it sends a positive acknowledgement back to the sending device 4. When the sending device receives the positive acknowledgement, it knows the receiving device has received the data packet error-free and sends the next data packet 5. If the sending device does not receive a positive acknowledgement within a set timeframe, a time out occurs 6. When a timeout occurs, the sending device will resend the data packet and will keep doing this until it receives a positive acknowledgement or until a set limit is reached
35
What is the process of the negative acknowledgement method?
1. Sending device transmits the first data packet 2. Receiving device receives the data and checks it for errors 3. If the receiving device detects no errors, no further action is taken 4. If the receiving device does detect errors, it will send a negative acknowledgement back to the sender 5. If the sender receives a negative acknowledgement, it knows the data was received incorrectly and resends the data packet 6. A timeout is set by the sending device when it sends the data so it knows that if it doesn't receive a negative acknowledgement back within that set time period, it doesn't need to still be waiting for it and can send the next data packet
36
What is a check digit?
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 digit values are compared to see if the data entered is correct.
37
What is the process of a check digit?
1. A check digit value is previously calculated from the data that will be entered (e.g. barcode number, ISBN number) and stores it with the data 2. When the data is entered, the check digit is recalculated from the data entered 3. If the previously calculated check digit and the stored check digit match, the data entered is correct 4. If the previously calculated check digit and the stored check digit do not match, the data entered is incorrect
38
What is encryption?
A method of securing data for storage or transmission that scrambles it and makes it meaningless.
39
What is plain text?
The name given to data before encryption.
40
What is an encryption key?
A type of algorithm that is used to encrypt data.
41
What is cipher text?
The name given to data after encryption.
42
What are the two main methods of encryption?
- Symmetric encryption - Asymmetric encryption
43
What is symmetric encryption?
A type of encryption that uses the same key to encrypt and decrypt data.
44
What is the process of symmetric encryption?
1. Plain text is encrypted into cipher text using an encryption key 2. The cipher text and the encryption key are sent separately to the receiving device 3. The same key is then used to decrypt the cipher text back into its plain text form
45
What is asymmetric encryption?
A type of encryption that uses two different keys to encrypt and decrypt data.
46
What is the process of asymmetric encryption?
1. Plaint text is encrypted into cipher text using a public key (this is also a type of encryption algorithm) 2. The cipher text is transmitted to the receiving device 3. The cipher text cannot be decrypted using the public key, it is decrypted using a private key

.Computer Science (7 decks)

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