Error Detection and Corrections

Error Detection and Corrections

Different types of errors can occur during the transmission of data in a network. Errors like bit altering, packet loss, data block missing, etc can occur. These errors occur due to the fault in hardware or some other network limitations. So, various methods should be applied for detection and correction of these errors to establish a perfect communication.

Error Detection

For a given frame, an error-detecting code (check bits) is calculated from data bits and it is appended to the data to send to a receiver. In the receiver side, the incoming frame is separated into data bits and check bits and calculates check bits from received data bits. Then the calculated check bits is compared against received check bits and error is detected. Different technique can be applied for error detection and they are:

Parity Checking:

It is the simplest technique for detecting the error. A parity bit is added in data bit. Then at the receiver side, the parity of data is compared with the parity bit for detection of error.

Checksum Error Detection:

In this technique, all the bytes in a message are added to generate a checksum which is then sent after all the messages. Then, when the receiver receives the message it separately calculates the checksum and compares with the one sent by the sender and detects error it no match occurs.

Cyclic Redundancy Check (CRC):

It is most powerful than Parity and checksum. It is based on division. A sequence of redundant bits called CRC is generated by dividing the data with some specific byte and is appended at the end of data which is used at the receiver side for error detection.

Error Correction

Error correction is the process of regeneration of actual data from a noisy or faulty data. However, over copper wire retransmission is faster than error correction but in the case of very noisy networks, without error-correction, it will be hard to get anything through. Error-correcting codes are widely used on wireless links, which are very noisy and error prone when compared to copper wire or optical fibers. Hamming code is one of the techniques used for error correction.

Reference

1. Tanenbaum, WetherRall, Andrew S. , David J. ,Computer Networks. 5th Ed. Boston: Pearson Education, Inc
2. W. Stallings, “Data and Computer Communication”, Macmillan Press, 1989.
3. Kurose Ross, “Computer Networking: A top-down approach”, 2nd Edition, Pearson Education
4. Larry L. Peterson, Bruce S. Davie, “Computer Networks: A Systems Approach”, 3rd Edition, Morgan Kaufmann Publishers