This read-only Integer32 (1..65535) uniquely identifies a row in the OAM flow point statistics table, where index 1 is the 15-minute bin, index 2 the 1-day bin, and index 3 the rollover bin. It gives an administrator a predictable way to fetch a specific aggregation window's Ethernet OAM statistics for this flow point without ambiguity about which bin is being read. For example, a management station polling index 2 for a given flow point retrieves that day's OAM error tally rather than the short-term 15-minute snapshot.