Data packets
Identify the three parts of a data packet
Head, trailer, payload
Data transferred in only one direction
Simplex
Identify three methods of error checking
Parity check
Checksum
Checkdigit
Echo check
ARQ
Identify the name given to data before encryption
Plain text
Identify three things contained in the header
IP address of the sender
IP address of the receiver
Packet number / order
Describe half duplex / serial data transfer (4 marks- 4 points)
Data in both directions
Not at the same time
One bit at a time
Down a single wire
Which of the following bytes have been transmitted incorrectly if we were using a parity check and why?
11110000
10101110
11110011
10101110
Uses an odd parity, the other two bytes use an even parity
Symmetric- uses the same key to encrypt and decrypt data
Asymmetric- uses two different keys to encrypt and decrypt data.
Why does data need to be broken down into packets to be transmitted?
Data such as images and videos can be too large to transfer, this will take a long time to transfer. Breaking down into packets will ensure data can be transferred faster.
Identify one advantage and one disadvantage of parallel data transmission
+ Quicker transmission
- Increased chance of data being skewed
- Multiple wires therefore more expensive than serial data transmission
A type of error detection method that uses acknowledgement and timeout to see if data has arrived correctly after transmission
ARQ
Describe the process for symmetric encryption- 3 points
Plain text is encrypted into cipher text using an encryption key
The cipher text and the encryption key are sent separately to the receiving device.
The same key is then used to decrypt the cipher text back into its plain text form.