This counts test frames received more than once, identified by the sequence number embedded in each RFC2544-style test frame repeating unexpectedly, which points to duplication somewhere in the forwarding path rather than simple loss. An admin treats duplicates as a distinct fault class from loss or reordering, since a device that duplicates frames (for example due to a Layer 2 loop or a faulty LAG hashing setup) can pass a naive throughput check while still corrupting the data stream. For example, cienaCesBenchmarkTestInstanceStatsRxDuplicatePkts incrementing steadily during an otherwise clean test would prompt the admin to check for a spanning-tree or multicast-flooding loop on the test path.