Alcatel-Lucent 7450 ESS-7 - Figure 13: Messaging Sequence between the PTP Slave Clock and PTP Master Clock; SONET;SDH Signals

System Management
7450 ESS OS Basic System Configuration Guide Page 235
SONET/SDH Signals
The SSM of SDH and SONET interfaces is carried in the S1 byte of the frame overhead. Each
frame contains the four bit value of the QL.