EXFO FTB-800 Series for FTB-1 - Manual (Page 273)

Test Results
NetBlazer 263
Alarms/Errors
IP/UDP/TCP
Errors

IP Chksum (IP Checksum)
RX: The IP datagrams received have invalid IP header checksum. Only
available for IPv4.

UDP Chksum (UDP Checksum)
RX: The UDP segments received have invalid UDP checksum.

TCP Chksum (TCP Checksum)
RX: The TCP segments received have invalid TCP checksum.
ISDN
Alarms

D-Ch Down (D-Channel Down)
RX: The Data Link Layer is not in the multiple-frame established state.
Errors

D-Ch FCS (D-Channel FCS)
RX: D-Channel Frames have an invalid FCS.