Packet LatencyΒΆ

TRex Traffic Generator (TG) is used for measuring latency across 2-Node and 3-Node SUT server topologies. TRex integrates A High Dynamic Range Histogram (HDRH) code providing per packet latency distribution for latency streams sent in parallel to the main load packet streams. Packet latency is measured using following methodology:

  • Latency tests are performed at following packet load levels:

    • No-Load: latency streams only.

    • Low-Load: at 10% PDR.

    • Mid-Load: at 50% PDR.

    • High-Load: at 90% PDR.

    • NDR-Load: at 100% NDR.

    • PDR-Load: at 100% PDR.

  • Latency is measured for all tested packet sizes except IMIX due to TG restriction.

  • TG sends dedicated latency streams, one per direction, each at the rate of 9 kpps at the prescribed packet size; these are sent in addition to the main load streams.

  • TG reports Min/Avg/Max and HDRH latency values distribution per stream direction, hence two sets of latency values are reported per test case.

  • Reported latency values are aggregate across tested topology.

  • +/- 1 usec is the measurement accuracy advertised by TRex TG for the setup used.

  • TG setup introduces an always-on Tx/Rx interface latency of about 2 * 2 usec per direction induced by TRex SW writing and reading packet timestamps on CPU cores.