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Spirent TestCenter: What is the behavior of the Routing convergence, RFC-6413 rate based convergence when there are drops?

  • Calculate the OSPFv2 convergence time using the routing convergence wizard.

  • DUT gives packet drops even at 10% and sequencer always fails during the test.

    • At 10% line rate, sequencer fails at “Setup Routing Convergence” step.

    • At 100% line rate, sequencer fails at “Wait for Data Plane Samples” step.

  • Questions

    1. Does traffic need to be sent at 100% line rate for the Wizard to work?

    2. Is the convergence time always calculated based on dropped frame counts? 

    3. Should there be no drops before the event occurs?


  • The existing Routing convergence wizard is based on Rate based convergence using RFC 6413.
  • In 4.47 we will be adding support for control plane convergence with trigger event timestamp measurement.
  • The DUT should not show packet loss at the start of the test.
    • In Rate based convergence, the test measures expected RX rate on the primary port before convergence.
    • Then after convergence trigger event, the traffic rate on backup port is  expected to reach within 95% of rate observed on the Primary port after the start of the test.
    • Then the test is considered converged.
  • During Setup Routing Convergence” the traffic rate is being sampled at the RX ports and there should be no loss.
    • Is there packet loss at the start of the test?
  • If sequencer fails at “Wait for Data Plane Samples” step, this implies rate on back up port is not reaching expected rate.
  • Regarding the questions:
    1. Any rate, not only100% can be used but  the lower the traffic rate the longer it will take to measure convergence.
    2. Convergence is calculated based on rate reaching expected rate  RFC 6413. 
    3. There should be no drops during rate sampling at the start of the test.
  • There is a new methodology in 4.47 for control plane trigger event base convergence.
    • This is not based on rate or loss.
    • This is based on trigger event timestamp and arrival time of each stream.

Product : Routing,Spirent TestCenter,OSPF