Synchronization Status Messaging; Figure 6-1 Ons 15600 Timing Example; Table 6-1 Ssm Generation 1 Message Set - Cisco ONS 15600 Series Reference Manual

Chapter 6 Timing
Figure 6-1
Node 4
Timing: Line
Ref 1: Slot 12, Port 1
Ref 2: Slot 11, Port 1
Ref 3: Internal (STE)

6.3 Synchronization Status Messaging

Synchronization Status Messaging (SSM) is a 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. They
enable SONET 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 set. Generation 2 is a newer version. If you enable SSM for the ONS 15600, consult your
timing reference documentation to determine which message set to use.
message set.
Table 6-1
Message
PRS
STU
ONS 15600 Timing Example
Slot 11
Port 1
Slot 12
Port 1
Slot 11
Port 1
Slot 12
Port 1
SSM Generation 1 Message Set
Quality Description
1 Primary reference source—Stratum 1
2 Synchronization traceability unknown
BITS1 BITS2
source source
Node 1
Timing: External
Ref 1: BITS1
Ref 2: BITS2
Ref 3: Internal (STE)
Slot 12
Port 1
Slot 11
Port 1
Slot 12
Port 1
Slot 11
Port 1
Node 3
Timing: Line
Ref 1: Slot 11, Port 1
BITS1 BITS2
Ref 2: Slot 12, Port 1
Out Out
Ref 3: Internal (STE)
Third party
equipment
Cisco ONS 15600 Reference Manual, R7.0
6.3 Synchronization Status Messaging
Node 2
Timing: Line
Ref 1: Slot 11, Port 1
Ref 2: Slot 12, Port 1
Ref 3: Internal (STE)
Table 6-1 lists the Generation 1
6-3