Computer Network: Throughput and Efficiency on SWP

Question

How to calculate window size in Stop and Wait, Select and Repeat, GBN.

Some where I have seen window size as w = 1+2a

where a = PT/TT.

and some where it is calculated as:

if we have

RTT = 160msec

BW = 256 Kbps

Data size  = 64Bytes

then window size as

[160 * 10^(-3) * 256 * 10^(3)]/(64 * 8)

which one to follow.

And how to calculate Throughput and Efficiency ib all three protocol u can take above configuration to derive result.

Please explian it.

Comments

yes.

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@joshi_nitish check this

Some where in the soln I have seen that processing time is also used to includes in the denomenator.

I think eff is transfer time of data packet div by total time which is tt of data and pt of data and tt of ack and pt of ack and processing of data and processing of ack

right??

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@ Shubhanshu yes you are correct, in total time we include all the delays which are possible during sending of a frame till getting the acknowledgement of that frame (or frames).

check this question, here explicitly all delays are given in the question https://gateoverflow.in/118328/gate2017-1-45

Also I saw at many places on Go that in RTT we include Transmission time also. check this https://gateoverflow.in/1820/gate2006-44

the round-trip delay time (RTD) or round-trip time (RTT) is the length of time 
it takes for a signal to be sent plus the length of time it takes for an acknowledgment 
of that signal to be received.

For your first query, we can use both approaches to find window size, depending on what metrics are given in the question.

• by using Window size WS = 1+2a or say using total time as TT+2PT, #packets= (TT+2PT)/TT
• by given bandwidth, RTT, Packet size, I can find number of packets as                                #packets=WS= (RTT*BW)/Packet size

Answer 1

this is how to find efficiency,throughput and window size

Comments

Is it will be directly given in the question or we have to calculate if it is not given in the question?

for both ack and data pkts.

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Processing time or any other extra information would be given directly i the question... You do one thing just analyze the previous year gate question, then you will get an idea.

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Thanks !!!