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Lets L = size of the packet and R = data rate of the whole path.
Average QD= MaxRTT - MinRTT.
Average TD = L/R
It is practically, impossible to get a very good estimate of Queing delay at each hop along the path using ping.
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Now get the Max and min rtt from the two sets separately. and denote it minRTT1, maxRTT1 for R1 and minRTT2 and maxRTT2 for R2.
It is simple to find queing delay at R1 which is:
Queing Delay at R1 (QD1) = maxRTT1 - minRTT1
As the packet goes, the latency from A to R2 is mainly affected by the queing delay of R1. Hence we need to subtract the queing delay at R1 from the difference of maxRTT2 and minRTT2.
Queing Delay at R2 (Qd2) = maxRTT2 - minRTT2 - Qd1
Hence Hence, Queing Delay of nth hop router (Rn) is given below:
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Qdn = (maxRTTn - minRTT2 minRTTn) - ? i=1 to n-1(Qdi) |
Infact queing delay is variable, and three RTTs are not enough to measure a good estimate of queing delay. In this case, we need to measure the analysis of like arround 10-100 RTTs to get a sufficient good estimate of queing delay. The more RTTs we have in a set for a router, the more better estimate we can fetch.