Which field in the IPv4 header helps uniquely identify fragments of a datagram so they can be reassembled correctly?
Explanation
When an IP datagram is larger than the Maximum Transmission Unit (MTU) of a network link, it must be broken into smaller pieces called fragments. To ensure the destination host can reassemble these fragments back into the original datagram, the IPv4 header contains specific fields to keep track of them.
Identification: This 16-bit field is unique for each original datagram sent by a host. When a datagram is fragmented, all fragments share the same identification number, allowing the receiver to group them together.
Flags: These indicate whether more fragments follow or if this is the last fragment.
Fragment Offset: This indicates the position of the fragment within the original datagram.
The relationship between the original datagram and its fragments can be represented as:
Fragment Group={Fragments with same Identification Value}
Reassembly Order={Sorted by Fragment Offset}
Because the Identification field acts as the unique identifier for all fragments belonging to a single original packet, it is the correct answer.
