6-4
Cisco ONS 15600 SDH Reference Manual, Release 9.0
78-18400-01
Chapter 6 Timing
6.3.1 SONET SSM Messages
6.3.1 SONET SSM Messages
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 SONET SSM for the
ONS 15600 SDH, consult your timing reference documentation to determine which message set to use.
and
show the SONET Generation 1 and Generation 2 message sets.
6.3.2 SDH SSM Messages
If you enable SDH SSM for the ONS 15600 SDH, consult your timing reference documentation to
determine which message set to use.
Note
Mapping from DS1 SSM to E1 SSM is possible when DS1 timing is used on the 15600 SDH platform.
shows the SDH SSM messages.
Table 6-1
SONET SSM Generation 1 Message Set
Message
Quality
Description
PRS
1
Primary reference source—Stratum 1
STU
2
Synchronization traceability unknown
ST2
3
Stratum 2
ST3
4
Stratum 3
SMC
5
SONET minimum clock
ST4
6
Stratum 4
DUS
7
Do not use for timing synchronization
RES
—
Reserved; quality level set by user
Table 6-2
SONET SSM Generation 2 Message Set
Message
Quality
Description
PRS
1
Primary reference source—Stratum 1
STU
2
Synchronization traceability unknown
ST2
3
Stratum 2
TNC
4
Transit node clock
ST3E
5
Stratum 3E
ST3
6
Stratum 3
SMC
7
SONET minimum clock
ST4
8
Stratum 4
DUS
9
Do not use for timing synchronization
RES
—
Reserved; quality level set by user