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Answer Key LEC02
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Q1

1. b
2. a
3. b
4. TCP

5. advantage: faster response time, lower load on the origin server
   disadvantage: might get outdated web pages

6. b

7. top-level domain servers keep a larger amount data because it keeps
   information of all domains ending with .com/.ca etc. Root name server
   keeps only info of the TLD servers

8. UDP
9. packet loss
10. ACK with the previous number

11. b

12. triple duplicate ACK, timeout

13. a

14. 256

15. Broadcast

16. checksum / fragmentation

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Q2

(a/b) Yes, converges to fairness after one decrease

(c) The average throughput is lower than AIMD because of the dramatic decrease.

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Q3

(a) 2 Gbps

(b) 

total transmission delay is 200Kb / 2Gbps + 200Kb / 5Gbps = 140 miscroseconds

propogation delay = 300 - 140 = 160 microseconds

distance = 2x10^8 * 160x10^-6 = 32,000 metre

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Q4

(a)

0123, 0, 2
0123, 0, 3
0123, 0, 4
1234, 1, 5
2345, 2, 6
2345, 2, 6
2345, 2, 6
2345, 2, 6

(b)

re-send 2, 3, 4, 5

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Q5

(a) [1, 6], [23, 26]

(b) 16, 22

(c) 32

(d) 8

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Q6

(a) 0, 1

(b) 

4 states
wait for 0 from A
wait for 0 from B
wait for 1 from A
wait for 1 from B

(c)

No, the senders have timers which are enough.