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Spirent TestCenter: Streamblocks reports very large false drop count.

When running 1000 flows with 2 different stream blocks the drop count shows 99.89% of packet loss but Tx and Rx count is 100%.
  • PX3 Yellowstone
RIT is only supported on Yellowstone performance mode.  Without RIT support on the default mode, there is no mechanism on the FPGA generator side to handle the sequence number so, invalid sequences are sent and causing the drop counts to occur.  Unfortunately, this is the design limitation since the PX3 Yellowstone default mode supports a maximum of 64 paths.

A solution for this issue is to change the port to performance mode.
Root Cause
This is related to path compression.  
  • When configured paths <=64, no path compression is needed, the FW writes all the information into the VFD1 and VFD6, and no drop count occurs.
  • When configured paths >64, the BLL will do the path compression (all the paths are compressed into one item for this configuration) and RIT should be enabled.  This item will be written to VFD6 and RIT (BAR1 + 0x16000).

Product : PX3,Spirent TestCenter