Although several error detection methods have been devised, only few are used in practice. Most of network systems send with data packeta a checksum so that receiver can detect errors properly. The sending side uses the data as series of integers and calculates their sum so that calculation of checksum should be accurate. The data is not restricted to integer values – it can contain characters, floating point numbers, or an image. The network system merely treats the data as a sequence of integers for purposes of computing a checksum. Checksums have advantages and disadvantages. The major advantages arise from the size and ease of computation.
Most networks that employ a checksum technique use a 16-bit or 32-bit checksum, and compute a single checksum for an entire packet. The small size of the checksum means the cost of transmitting the checksum is usually much smaller that the cost of transmitting the data. Furthermore, because checksums only require addition, the computation required to create or verify a checksum is small. Checksums have the disadvantage of not detecting all common errors. For example a checksum is not sufficient to detect a transmission error that receives a bit in each item data item. Despite the changes a receiver will declare that the packet has a valid checksum.
Most networks that employ a checksum technique use a 16-bit or 32-bit checksum, and compute a single checksum for an entire packet. The small size of the checksum means the cost of transmitting the checksum is usually much smaller that the cost of transmitting the data. Furthermore, because checksums only require addition, the computation required to create or verify a checksum is small. Checksums have the disadvantage of not detecting all common errors. For example a checksum is not sufficient to detect a transmission error that receives a bit in each item data item. Despite the changes a receiver will declare that the packet has a valid checksum.