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Spirent TestCenter: How Spirent TestCenter calculates IGMP/MLD join/leave latency?

Environment/Versions
  • Spirent TestCenter
  • IGMP/MLD
Answer
  • Please find attached document on how Join/Leave latency in IGMP/MLD are calculated
  • There are certain scenarios where the join/leave latencies seem "weird".  Please refer to
         FAQ17420 - Spirent TestCenter: Why am I seeing weird join/leave latency measurements?
  • DX type modules 
    • When using VLANs, Join/Leave altency is not supported.
      • Reason:
        • A 16-bit analyzer filter is enabled on VLAN. However, stream Rx results were not subscribed at all because of this 16-bit filter.
          Even if removing the 16-bit VLAN filter before starting sequencer, it was automatically be added when joining multicast groups. 
          It is required by Multicast Latency Calculation that a 16-bit filter should be on VLAN if VLAN exists.
      • Root cause:
        • Hardware limitation.
          VLAN filter was added by Multicast latency calculation when joining the multicast group. 
          However, DX modules do not support analyzer filter except on Spirent Signature. Therefore, the stream results will all be 0.
          MX/FX does not have this issue, because VLAN filter is supported by these module.
      • Solution:
        • Only solution is for a Warning message.
          For DX*- modules a warning will indicate "analyzer filter other than Spirent Signature exists".

Product : Access,Spirent TestCenter,IGMP/MLD