Which of the following best describes the purpose of the 'Fragment Offset' field in the IPv4 header?

The 'Fragment Offset' field in the IPv4 header serves a crucial role in managing fragmented packets during transmission. When an IP packet is too large to be transmitted over a network with a smaller Maximum Transmission Unit (MTU), it must be broken into smaller chunks called fragments. The Fragment Offset field indicates the position of each fragment within the original, larger packet.

This position is specified in units of 8 bytes, which means it tells the receiving device where to place the fragment in the context of the complete data set being reassembled. By using this field, the receiving device can correctly piece all the fragments together in the proper order, ensuring that the original data is reconstructed accurately. This is essential for the integrity of data communication, as it allows fragmented packets to be reassembled seamlessly.

The other options describe different aspects of the IP header but do not accurately reflect the function of the Fragment Offset field. Identifying the type of service or specifying the size of the packet are handled by other fields in the header, while denoting the priority level does not pertain to the Fragment Offset's purpose.