TCPUDPPrüfsummen

TCPUDPPrüfsummen, or TCP/UDP Checksums, are a mechanism used in the Transport Layer protocols TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) to detect errors in transmitted data. The checksum is a small value calculated by the sender based on the contents of the TCP or UDP header and the data payload. This calculated value is then included in the checksum field of the header.

When the receiver receives a segment, it independently calculates the checksum of the received header and data using the same algorithm. It then compares its calculated checksum with the checksum value provided by the sender in the header. If the two values match, it indicates that the data has likely arrived without errors during transmission. If the values do not match, the receiver can infer that the data has been corrupted and typically discards the segment.

For UDP, if an error is detected, the datagram is usually discarded by the operating system without notification to the application. TCP, being a reliable protocol, has a more robust error-handling mechanism. If a TCP checksum error is detected, the receiver will not acknowledge the corrupted segment, and the sender will eventually retransmit the data. The checksum calculation is a crucial part of ensuring data integrity over potentially unreliable network connections.