Applied Mock Test 2

Question

In TCP, MSS is 8B. If during the 6th RTT the network is congested and timeout occurs, by using the congestion algorithm, then the threshold value is _________(in Bytes). (assume initial congestion window size for the first transmission is 1 MSS)

Comments

Ans is 256 Bytes?

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I guess it should be 128 Bytes

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@Yaman Sahu how ? can u write sequence…

 

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1,2,4,8,16,32,64(TO occurs)

therefore, threshold = 64/2 = 32 MSS = 32 * 8= 256 Bytes

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@Yaman Sahu they also given mss 8  where we use this?

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therefore, threshold = 64/2 = 32 MSS = 32 * 8= 256 Bytes

 to calculate in Bytes

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@LRU, @jugnu1337 Refer this question

https://gateoverflow.in/1794/Gate-cse-2014-set-1-question-27

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How are you justifying the sentence "During the 6th RTT, Will you please elaborate?

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@Vishal_kumar98 Refer above question link first it explains in detail

1,2 means After 1RTT, cwnd = 2MSS (count ‘,’) 

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@yaman sahu they have asked for time out at 6^th not after 6^th so your provided solution should have 16*8=128 

Answer 1

1st transmission:   1 MSS
2nd transmission:  2 MSS

3rd transmission:   4 MSS
4th transmission:   8 MSS

5th transmission:  16 MSS

6th transmission:  32 MSS [ Window th = 32 / 2 =  16 MSS]

16 MSS = 16 * 8 = 128  B

Comments

@Vishal_kumar98 what will be the congestion threshold for slow start?

Answer 2

1MSS----(RTT)-->2MSS—(RTT)---->4MSS----(RTT)-->8MSS---(RTT)--->16MSS----(RTT)-->32MSS------>Timeout

Final CWND  = 32

Threshold value = 32/2 = 16 MSS = 16*8 bytes = 128 Bytes