Question

MIDTERM REVIEW.

PLEASE EXPLAIN EVERY STEP AND SHOW FORMULA'S TO CALCULATIONS!!!!!

THANKS

9. Fragmentation. (1) Consider the network in the figure below, where the MTUs (in Bytes) of the link layers for the three hops is listed. These MTUs include the header of the packets. The header size is 20 bytes LL1 MTU 1500B LL2 MTU 700B LL3 MTU 350B link ab offset 1420 (1400) 45654 700 (680 700 (680) 60 (40) 350 (330) 45654 350 (330 40 (20 350 (330) 45654 350 (330) 45654 40 (20 60 (40) 45654 45654 45654 680 1360 45654 45654 330 660 680 1010 1340 1360 45654 45654 (2) Where are fragments reassembled? Can they be reassembled anywhere else? Why or why not?

Answer 1

Dear student, according to the given Question,

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Note: 2nd Diagram is in landscape mode

2) Where the fragments reassembled? Can they be reassembled anywhere else? Why or Why not?

Once the packet is fragmented, the reassembling must be done at the destination only because of the following two reasons:

1. Different networks may have different MTU sizes: So, consider the question, if I reassemble at C, again I need to fragment them to transfer through C to D because the C to D MTU is different. So doing the rework (Fragmenting and reassembling)

2. All fragmented datagrams may not follow the same route: This is a valid point because the fragments follow different order and may be delayed during transmission. So upon getting all the fragments at the destination, Its better to Re-assembling at the destination.

Therefore, Reassembling must b done at destination node only Here at node D

I hope this much explanation will give you knowledge on this question.

If at all any doubts, feel free to comment on this. All the best