This counts the subset of received IPv4 packets that were specifically UDP, giving finer visibility than the general IPv4 counter when the benchmark traffic is generated as UDP datagrams (the typical choice for RFC2544 test streams because it avoids TCP retransmission skewing loss measurements). An admin compares this to cienaCesBenchmarkTestInstanceStatsRxIpv4Pkts to confirm that essentially all the IPv4 traffic received really is the UDP test stream and not some other IPv4 traffic leaking into the test path. For example, if RxIpv4Pkts and RxIpv4UdpPkts read nearly identical values, the operator confirms the test stream integrity is intact end to end.