This counts unicast frames received on this interface, the traffic class that carries real point-to-point service traffic. Because unicast dominates genuine inbound user and service traffic, this is the counter to graph over time for this specific port's receive side when sizing its traffic pattern or validating a change, rather than the broadcast or multicast counters on the same interface. For example, RxUcastPkts on this port dropping sharply for this in-progress short-interval bin right after a customer circuit was supposed to go live would be the first indicator inbound traffic isn't actually arriving yet.