Error Detection

Seite 1

Explain how checksums can be used to detect errors in data transmission

A checksum function is applied, to a number of bytes/a block of data. The checksum is sent as part of the data, it is recalculated after data transmission. If the checksum is incorrect, there is an error in the data. The data can be retransmitted. Some type of checksum may automatically correct the error.

If even parity is being used, explain the errors in each of the following bytes 10101011 and 10101010

In 10101011 the number of 1s is odd/the parity id odd, so one bit has flipped. In 10101010 the number of 1s is even, so two bits have flipped.

01101010 includes a parity bit, an error occurs when this byte is transmitted and it is received as 01101110. Describe how this error will be detected, and explain the consequences if the byte is received as 00001010

Even parity is being used, while the received bytes parity is odd. The double error will not be detected in 00001010 as the bytes parity is still even.

Name and describe one other way of detecting errors in data transmission.

Echo checking