From: gladston@br.ibm.com
Date: Thu May 26 2005 - 15:38:28 GMT-3
This is the best explanation I found about SAA jitter results.
But I could not understand how it get 14ms. Can you?
Specifically, I did not get this: "If you subtract the square of the average from this value and take the square root"
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Quoted from Cisco CookBook
Router1#show rtr operational-state 20
Current Operational State
Entry Number: 20
Modification Time: 10:25:36.000 EST Wed Dec 18 2002
Diagnostics Text:
Last Time this Entry was Reset: Never
Number of Octets in use by this Entry: 1742
Number of Operations Attempted: 22
Current Seconds Left in Life: 93400
Operational State of Entry: active
Latest Operation Start Time: 12:10:36.000 EST Wed Dec 18 2002
RTT Values:
NumOfRTT: 98 RTTSum: 6063 RTTSum2: 384317
Applying some simple statistics, you can use the square value to understand how the actual values are spread around this average. The mean of the squares of the round trip times is 3,922 milliseconds2 (just dividing the sum of the squares by the total number of samples). If you subtract the square of the average from this value and take the square root, you get a statistical estimate of the variation in milliseconds. The higher this value, the greater the spread. In this case, you can calculate that this spread is roughly 14 milliseconds. This means that half of the time, the round trip latency is within the range 61114ms. Note that the 1 symbol is a standard mathematical notation that, in this case, indicates a range from 47ms (61-14) to 75ms (61+14).
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quoted
If you subtract the square of the average from this value and take the square root, you get a statistical estimate of the variation in milliseconds... In this case, you can calculate that this spread is roughly 14 milliseconds.
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