EXFO IQS-8100 Series Transport Blazer for IQS-600 - Manual (Page 651)

Glossary
SONET/SDH Application 637
SDH - Multiplex Section Overhead (MSOH)
K1 and K2: APS Channel (Automatic Protection
Switching)
The K1 and K2 bytes communicate APS between two LTEs. This byte is
only defined for the first STM-1 frame of an STM-N signal.
D4 through D12: MS DCC (Data Communications
Channel)
The D4 through D12 bytes provides a 576 kbps data communications
channel between two LTEs for administration, monitoring and other
communications. These bytes are only defined for the first STM-1 frame of
an STM-N signal.
S1: SSMB (Synchronization Status Message Byte)
Bits 5 to 8 of the S1 byte are used to carry the synchronization messages of
the SDH device. This byte is only defined for the first STM-1 frame of an
STM-N signal.
M1: MS-REI (Remote Error Indicator)
The M1 byte of a STM-1 or the first STM-1 of an STM-N signal is used for MS
layer Remote Error Indication (MS-REI). This byte is located in the third
STM-1 of an STS-N signal (N > 1).
E2: MS Orderwire
The MS Orderwire provides a 64 kbps voice channel for communication
between LTEs. This byte is only defined for the first STM-1 frame of an
STM-N signal.