Specifications

3-14
Cisco ONS 15454 Installation and Operations Guide, R3.2
March 2002
Chapter 3 Node Setup
Setting Up ONS 15454 Timing
Procedure: Set Up ONS 15454 Timing
Step 1 From the CTC node view, click the Provisioning > Timing tabs (Figure 3-9).
Step 2 In the General Timing section, complete the following information:
• Timing Mode—Set to External if the ONS 15454 derives its timing from a BITS source wired to the
backplane pins; set to Line if timing is derived from an OC-N card that is optically connected to the
timing node. A third option, Mixed, allows you to set external and line timing references. (Because
Mixed timing may cause timing loops, Cisco does not recommend its use. Use this mode with care.)
• SSM Message Set—Choose the message set level supported by your network. If a Generation 1 node
receives a Generation 2 message, the message will be mapped down to the next available Generation
1. For example, an ST3E message becomes an ST3.
• Quality of RES—If your timing source supports the reserved S1 byte, you set the timing quality here.
(Most timing sources do not use RES.) Qualities are displayed in descending quality order as ranges.
For example, ST3<RES<ST2 means the timing reference is higher than a Stratum 3 and lower than
a Stratum 2. See Table 3-4 and Table 3-5 for more information.
Table 3-4 SSM Generation 1 Message Set
Message Quality Description
PRS 1 Primary reference source – Stratum 1
STU 2 Sync 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 3-5 SSM Generation 2 Message Set
Message Quality Description
PRS 1 Primary reference source - Stratum 1
STU 2 Sync 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