EXFO FTB-8510B Guia Del Usuario página 973

For STM-4: The MS-REI error is declared when the M1 byte located in
the STM-1 channel 3 (timeslot #7) indicates that one or more BIP
violations have been detected.
For STM-16: The MS-REI error is declared when the M1 byte located in
the STM-1 channel 3 (timeslot #7) indicates that one or more BIP
violations have been detected.
SONET/SDH Application
M1, bits
234 5678
000 0000
000 0001
000 0010
:
110 0000
110 0001
:
111 1111
M1
0000 0000
0000 0001
0000 0010
:
1111 1111
SDH Tabs
Multiplex Section RX (SDH)
Indicates
0 BIP violation
1 BIP violation
2 BIP violations
:
96 BIP violations
0 BIP violation
:
0 BIP violation
Indicates
0 BIP violation
1 BIP violation
2 BIP violations
:
255 BIP violations
323