error checking methods of data transmission

Question 1

what can parity checks be ?

Answer 1

they can be even (even number of bits) or odd (odd number of bits)

Question 2

state two states when parity check wouldn’t work

Answer 2

when two bits are interchanged

when there are multiple errors in the same byte

Question 3

what is Automatic Repeat Request?

Answer 3

it uses acknowledgement to indicate data receiver correctly

it also uses a timeout

Question 4

what is timeout in automatic repeat request

Answer 4

it is the time allowed to pass before the acknowledgement is received

Question 5

what is checksum

Answer 5

the checksum is based on the number of bytes in the block of data

Question 6

what happens when the checksum at the receiver’s end doesn’t match the checksum at the end of the data block?

Answer 6

error in the transmission occurs

Question 7

how does checksum work

Answer 7

a value is calculated from the data, it is transmitted with the block of data. The value is recalculated after transmission. Values are then compared after transmisson to check for any errors

Question 8

how does check digit work

Answer 8

a digit is calculated from the data, it is then added to the data. Digits are recalculated when data is entered and then digits are compared to check for any errors.

Question 9

what happens if an acknowledgement isn’t sent back before timeout occurs?

Answer 9

the message is automatically resent