In an IPv$4$ Packet header, the Identification field contains a unique identifier for each packet; however, packets are sometimes fragmented further by routers to transverse a network that supports a smaller packet size. What happens to the value of the Identification field in a packet header if the packet is further fragmented?

The unique ID for the packet is maintained, but for each fragment, a prefix is added to the original value.

The unique ID for the packet is maintained, but for each fragment, a suffix is added to the original value.

The unique ID is discarded, and completely new IDs are inserted in the Identification field for each of the fragments of the original packet.

Each fragment of the original packet maintains the original ID value in the header Identification field