Final answer:
In IP fragmentation of a 4KB datagram for a 1.5KB MTU link, the identification field remains the same (x) for all fragments. Offset and more fragments (MF) flag values are calculated based on data positions and fragment sequence, resulting in 3 fragments with appropriately set fields.
Step-by-step explanation:
The student's question pertains to the fragmentation of an IP datagram in the context of data transmission over a network. An original IP datagram of size 4KB (4096 bytes) exceeds the maximum transmission unit (MTU) of a link that allows a frame size of only 1.5KB (1500 bytes); therefore, fragmentation is required. The value of the identification field remains the same (x) for all fragments to ensure that the receiving system can reassemble the datagram correctly. However, the offset field will be different in each fragment, indicating the position of the fragment data in the original datagram. The more fragments (MF) flag is used to indicate if additional fragments are following. In this case, there will be three fragments.
The first fragment will have an offset value of 0 (since it starts at the beginning of the datagram), and the MF flag will be 1 (true) indicating more fragments will follow. The total length field will be 1480 bytes of data plus 20 bytes of header, totaling to 1500 bytes. The second fragment will also have a size of 1500 bytes, with the offset value being 185 (1480 bytes / 8), assuming the units for the offset field are in 8-byte blocks, and the MF flag will again be set to 1.
The third and last fragment will carry the remaining data, therefore, its size will differ (assuming it's less than the remaining available 1480 bytes of data space). The MF flag will be set to 0 (false), indicating no more fragments. The offset for the third fragment would be 370 (2 x 1480 / 8).