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Definition of Instantaneous Throughput 

Instantaneous Throughput is defined as the bits successfully received in the averaging window divided by the averaging window size (in time units). It is measured every averaging window.

Each value of the computed instantaneous throughput represents one point in the throughput plot. The computation and plotting are done every second of virtual simulation time. The source data file (for the plots) has in the 1st column the Timestamp and in the 2nd column, the Bytes transmitted. NetSim computes and plots the instantaneous throughput from this. For example, if the averaging window were 25ms, and if the source data entries were per the table below

Time (ms)












then the Instantaneous Throughputs,  (in Kbps since we have milliseconds in the denominator) would be 

  • First 25ms (1 to 25) 
  • Next 25ms (26 to 50  
  • Next 25ms (51 to 75)  

Link Throughput

The link throughput considers the entire traffic that was sent through a link. It includes data packets and control packets and includes retransmission, errors, or collisions. This would also include packet flows from multiple applications that may flow through the same link. Also, note that the packet size at the link (physical layer) is the packet size at the application layer plus overheads added by different layers in the stack.

The following formula is used to calculate link throughput in NetSim:

Application ThroughputThe application throughput only considers those data packets (application layer packet size) that were sent from the source and that were successfully received at the destination.

The following equations are used to calculate the application throughput in NetSim:

If Simulation Time > Application End Time, then

If Simulation Time < Application End Time, then


Obtaining instantaneous Link and Application throughput plots 

Enable the Plots option in the design window. Here users can choose the applications and links for which throughput plots are to be generated, as shown below:



Post simulation, the source data can be accessed from the plot window using the source data button as shown below:

The source data files can also be found in the saved directory of the experiment as shown below:


Graphical user interface

Description automatically generated


Related Articles:

On calculating jitter

On calculating latency