Guest Author - Cathy Spearmon
Computers on a network must be able to detect when data packets have been damaged in transmission. In order to detect these errors, computers on an Ethernet network attach a special code to each of its packets. When the Ethernet packets are created, the sending computer runs the data through a special mathematic formula and attaches the result called a Cyclic Redundancy Code, or CRC to the packet. The receiving computer then opens the packet, performs the same calculations and compares its answer with the answer included with the packet. If the CRC codes do not match, then the receiving computer asks the sending machine to retransmit the packet again. By keeping the packets small, this reduces the time that is required to retransmit the data following an error.