This counter records the number of unicast packets received on this Ethernet port during the archived historical interval. A historical drop in unicast reception helps the admin date exactly when a subscriber's device went idle or a link-layer issue began suppressing normal traffic. For example, if a customer says their connection stopped working sometime yesterday afternoon, the admin would step through the afternoon's cmEthernetTrafficPortHistoryESUP bins to find the exact interval where unicast traffic dropped to zero.