Abstract: In a packet transmission system that uses checksums, partial checksum calculations may be performed during periods of processor underutilization while the data is awaiting final output processing for transport. A system wide checksum service process may coordinate checksum calculations across multiple network protocol layers. The checksum calculations for the buffered data may be performed according to a priority assigned to the buffered data. For example, buffered data whose transmission is imminent may have a higher priority than buffered data that will be transmitted at a later time. Applications that generate data for transmission may register those portions with the service for checksum calculation. To simplify the process, a metadata structure may be created for the data portion, and used to manage the checksum calculations.