Methods for Error Detection in Packet Transfer:

Methods for Error Detection in Packet Transfer:

While we data transfer from one end to another , because of various reason the data cant be modified / Tampered . So receiver should know if any error happened during transmission .

Methods Applied for Error Detection :

1.     Parity BIT CHECK

2.     Check Sum

Parity Bit Check(Even –Bit parity Check )

1.     A parity bit is added to a data packet for the purpose of error detection

2.     In the even-parity convention, the value of the parity bit is chosen so that the total number of '1' digits in the combined data plus parity packet is an even number. 

3.     Upon receipt of the packet, the parity needed for the data is recomputed by local hardware and compared to the parity bit received with the data.

4.     If any bit has changed state, the parity will not match, and an error will have been detected

5.     In fact, if an odd number of bits (not just one) have been altered, the parity will not match.

6.     If an even number of bits have been reversed, the parity will match even though an error has occurred. However, a statistical analysis of data communication errors has shown that a single-bit error is much more probable than a multibit error in the presence of random noise.

Check Sum Method:

1.     In this case, the packets that constitute a message are added arithmetically.

2.      A checksum number is appended to the packet sequence so that the sum of data plus checksum is zero

3.     When received, the packet sequence may be added, along with the checksum

4.     If the sum is nonzero, an error has occurred.