Cisco Systems 15454M6DC Manual De Usuario

3-14

Cisco ONS 15454 Installation and Operations Guide

November 2001

Chapter 3 Node Setup

Setting Up ONS 15454 Timing

3.6.2 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 message set. Generation 2 is a newer version. If you enable SSM for the ONS 15454,
consult your timing reference documentation to determine which message set to use.

Table 3-4

and

Table 3-5

show the Generation 1 and Generation 2 message sets.

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:

Table 3-4

SSM Generation 1 Message Set

Message

Quality

Description

PRS

Primary reference source – Stratum 1

STU

Sync traceability unknown

ST2

Stratum 2

ST3

Stratum 3

SMC

SONET minimum clock

ST4

Stratum 4

DUS

Do not use for timing synchronization

RES

Reserved; quality level set by user

Table 3-5

SSM Generation 2 Message Set