Cisco Systems 78-16845-01 manual Setting Up External or Line Timing for CTC-Based SDH NEs

Chapter 3 Building the Network

3.10.2 Synchronization Settings for the ONS 15454 SDH and ONS 15600 SDH

3.10.2 Synchronization Settings for the ONS 15454 SDH and ONS 15600 SDH

SSM communicates information about the quality of the timing source. SSM messages are carried on the S1 byte of the SDH section overhead. These messages enable 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 SDH, consult your timing reference documentation to determine which message set to use. Table 3-20shows the SDH message set.

Table 3-20	SDH SSM Message Set
Message		Quality	Description
G811		1	Primary reference clock
STU		2	Synchronization traceability unknown
G812T		3	Transit node clock traceable
G812L		4	Local node clock traceable
SETS		5	Synchronous equipment
DUS		6	Do not use for timing synchronization

Note Alarms relating to PM collection indicate that the load on the system is high. Reduce the load on the system before proceeding.

3.10.2.1 Setting Up External or Line Timing for CTC-Based SDH NEs

Step 1 Select an ONS 15454 SDH or ONS 15600 SDH NE and choose Configuration > NE Explorer.

Step 2 In the node property pane, select the Timing tab. Fields shown depend on the NE that is selected.

Step 3 In the General Timing section of the General subtab, complete the following information:

•Timing Mode

–For the ONS 15454 SDH:

Choose External if the ONS 15454 SDH NE derives its timing from an MIC-C/T/P FMEC; choose Line if timing is derived from an STM-N card (non-DWDM node) or OSC card (DWDM node) that is optically connected to the timing node. A third option, Mixed, allows you to set external and line timing references.

–For the ONS 15600 SDH:

Choose External if the ONS 15600 SDH NE derives its timing from a BITS source wired to the backplane; choose Line if timing is derived from an STM-N card that is optionally connected to the timing node. A third option, Mixed, allows you to set external and line timing references.

Caution Because mixed timing may cause timing loops, Cisco does not recommend its use. Use this mode with care.

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