Andrew S. Tanenbaum Edition 5th Exercise 5 Question 36 (Page No. 494)

Question

Describe a way to reassemble IP fragments at the destination.

Comments

by using the identification number and fragment offset

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by using the identification number we can determine that fragment belong to which  packet

and by using the offset  we can determine the sequence of the fragments of that particular packet

Answer 1

For Reassembling the IP datagrams at Receiver side ---

 

Step1: The first fragment can be distinguished by the offset:0 and the last offset can be distinguished by M-bit ‘0’.

Step2: All we have is to pick each fragment, so they are identified by an identification number calculated by it corresponding offset.

Step3: We repeat this step-3 until we reach last fragment.

Answer 2

One way to reassemble IP fragments at the destination is to use the identification field in the IP header. Each fragment will have the same identification value, and the destination can use this value to group the fragments together. Additionally, the fragment offset field in the header can be used to determine the correct order of the fragments. Once all of the fragments have been received, they can be reassembled in the correct order and the original packet can be reconstructed.