What does a checksum help to ensure during data transmission?

A checksum is a value used to verify the integrity of a dataset during transmission. It is calculated from the data before transmission and sent alongside it. When the data is received, the checksum is recalculated. If the newly calculated checksum matches the original, it indicates that the data has not been altered, corrupted, or lost during transmission. Therefore, it helps ensure data accuracy.

The mechanism of a checksum is fundamental in various networking protocols and file transfer methods to maintain reliability and accuracy in data communication, making it a critical tool for error detection. When a mismatch occurs, it can signal that issues arose during the data's journey, prompting a retransmission or alert to the user.

The other choices relate to aspects that do not directly connect to the primary function of a checksum. For instance, while increased speed or resource optimization can be beneficial in data transmission scenarios, they are not the primary purpose of a checksum, which is focused on ensuring that the received data is an accurate copy of the transmitted data. Similarly, access control pertains to permissions and user authority over data, which also does not relate to the checksum's role in maintaining data integrity.