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Spirent TestCenter: What is the difference between Step and Burst Mode?

Environment/Versions
  • STC all releases
  • Traffic Generator
  • Step duration Mode
  • Burst duration Mode
Answer

This will be explained using a config with the following details:

  • 10 stream blocks
    • Length of each increments by 1 bytes starting from 64 bytes
    • We can use this in the pcap to easily see what stream block is being tx/rx

 

  • BURST MODE:
    1. Here we use a step of 9
    2. We start the generator
    3. Wait a few seconds (so that you can see a gap in the timestamp in Wireshark)
    4. Start the generator again
    5. Here is the resultant pcap
      • note how the 10th packet, which is the first one from step 4, is 64 bytes
      • This means the generator starts at the top of the stream blocks, that is, stream block with index 0

 
 

  • Step mode:
  1. Here we use a step of 9
  2. We start the generator
  3. Wait a few seconds (so that you can see a gap in the timestamp in Wireshark)
  4. Start the generator again
  5. Here is the resultant pcap
    • note how the 10th packet, which is the first one from step 4, is 73 bytes.
    • This time the generator will start off where it left off after step 2
    • Also note that if you change any parameter in the generator, the starting point of the next “start generator” will be back at stream block index 0.


 

Product : Spirent TestCenter,Traffic Generation,Generator/Analyzer