This read-only Gauge32 counts AAL5 CRC errors related to upstream traffic from this specific ComPort during the current 15-minute period, with the description noting each such error represents a dropped Ethernet frame. It tells an administrator whether a particular subscriber's ATM-layer upstream path is corrupting data. For example, a technician investigating one customer's dropped connections would check this counter to see if AAL5 CRC errors are silently discarding that ComPort's upstream frames.