How many bits is the 'Checksum' field in the IPv4 header?

The Checksum field in the IPv4 header is 16 bits long. This field plays a crucial role in ensuring data integrity as it helps in error-checking the header of the IP packet. When an IP packet is created, a checksum value is calculated based on the contents of the header. This value is then placed in the Checksum field. When the packet reaches its destination, the receiving device will recalculate the checksum using the same algorithm and compare it to the value in the Checksum field. If the two values match, it signifies that the header has not been corrupted during transmission.

The size of 16 bits allows for a range of values that can effectively cover the needs for error detection in the relatively small header size of IPv4 packets. The other options propose sizes that do not correspond to the actual size of the Checksum field in the IPv4 header, which is strictly defined by the IPv4 protocol specifications.