Can some one please let me know the exact mathematical definition of jitter in packet networks ? Some RFCs indicate it as packet delay variation ? Is this variation to calculated among consecutive packets or for all the packets ?
Also does some one know to calculate this is NetSim simulator? It is not directly available in the results window ?
Time dependent variation in received signal is a regular phenomenon in radio communication because of multi-path propagation effects. The rate of variation of signal is classified as jitter if the rate is more than 10 Hz and as wander if the frequency is less than 10 Hz.
So, jitter is to be calculated over a period of time enough to consider more than 10 cycles.Averaging over a good number gives reliable idea about the long term variation.
Hence, adequate number of packets should be considered.
I do not work much with the simulator but I feel NetSim has the provision to vary jitter values to check the performance.
Jitter in IP networks is the variation in the latency on a packet flow between two systems, when some packets take longer to travel from one system to the other.
Three ways to measure jitter
Taking into account RFC 4689, the calculation of jitter requires measurement of the following four parameters:
Transmit time of the first packet in the pair.
Receive time of the first packet in the pair.
Transmit time of the second packet in the pair.
Receive time of the second packet in the pair.
In NetSim jitter can be only seen on a real video streaming.
In application properties you can set the above parameters.
NetSim help is available for calculation of jitter and the document is available at http://www.tetcos.com/File_Exchange/Help/NetSim-v10-help-delay-jitter-throughput-eventtrace.docx
Dear Rahul,
The colleagues above gave a satisfactory answer to your question but i want to stress some basic principles:
Jitter concerns statistical variations of theoretically regular occurrence of certain event.
For example the period time of an oscillator. If the oscillator is ideal then its pulses will be very strictly eqi spaced in time, however, this will never physically occurs because there is statistical factors affecting the periodic time such as the noise signal which varies the zero crossings of the deterministic waveform.
Like wise the time jitter of the average delivery time of the packets in a packet switched networks. Because the packets transport in packet switched network has statistical nature therefore the packet delivery will not be strictly regular. The delay gitter may be defined by the standard deviation of the delay from an average value.
It is calculated as it is defined.
best wishes
If you are familiar with NS2 trace file format,,, the following awk script might help you understand about the jitter.
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