Internetworking Technology

Dear all! To ensure the data transmitted in a network has no errors, an error detection and correction technique has to be employed. The errors caused by the noise during transmission can be detected by an error detection system and rectified and original signal is reconstructed by an error correction system.

There are several methods to construct an error detection system. Repetition code technique repeats the bits to be transmitted again and again to ensure an error free communication. Parity bits technique introduces an additional bit with the original data to ensure the number of bits. But this can able to detect only the odd number of bits that are incorrect.

Checksum technique produces an arithmetic sum of the message code words of finite word length. Cyclic Redundancy Check (CRC) technique uses a long division operation in which the remainder gives the result while the quotient is discarded. For error correction, the way to go is retransmission. But the type of request varies in different techniques.

In automatic repeat request an acknowledgement message is from the receiver is sent to transmitter after the receiver has correctly received the data. Otherwise the transmitter will resend. Forward error correction technique employs the addition of redundant codes with the original data and can be recovered at the receiver. Here no retransmission is required and hence this is well suited for simplex communication.

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