Cisco Cisco ONS 15454 M2 Multiservice Transport Platform (MSTP)
Synchronization Status Messaging
Synchronization status messaging (SSM) is a SDH and SONET protocol that communicates information about the quality of the
timing source. SSM messages are carried on the S1 byte of the SONET Line layer or on S1 byte of the SDH section overhead. They
enable SONET or SDH devices to automatically select the highest quality timing reference and to avoid timing loops.
timing source. SSM messages are carried on the S1 byte of the SONET Line layer or on S1 byte of the SDH section overhead. They
enable SONET or SDH devices to automatically select the highest quality timing reference and to avoid timing loops.
SSM messages are either Generation 1 or Generation 2. Generation 1 is the first and most widely deployed SSM message set.
Generation 2 is a newer version. If you enable SSM for the ONS 15454 or the ONS 15454 SDH , consult your timing reference
documentation to determine which message set to use.
Generation 2 is a newer version. If you enable SSM for the ONS 15454 or the ONS 15454 SDH , consult your timing reference
documentation to determine which message set to use.
The following table shows the SDH message set.
Table 1: SDH SSM Message Set
Description
Quality
Message
Primary reference clock
1
G811
Sync traceability unknown
2
STU
Transit node clock traceable
3
G812T
4