user manual
Table Of Contents
- Cisco ONS 15454 SDH Reference Manual
- Contents
- About this Guide
- Shelf and FMEC Hardware
- Common Control Cards
- Electrical Cards
- Optical Cards
- Ethernet Cards
- Storage Access Networking Cards
- Card Protection
- Cisco Transport Controller Operation
- Security and Timing
- Circuits and Tunnels
- SDH Topologies and Upgrades
- CTC Network Connectivity
- Alarm Monitoring and Management
- Ethernet Operation
- Hardware Specifications
- A.1 Shelf Specifications
- A.2 SFP Specifications
- A.3 General Card Specifications
- A.4 Common Control Card Specifications
- A.5 Electrical Card and FMEC Specifications
- A.5.1 E1-N-14 Card Specifications
- A.5.2 E1-42 Card Specifications
- A.5.3 E3-12 Card Specifications
- A.5.4 DS3i-N-12 Card Specifications
- A.5.5 STM1E-12 Card Specifications
- A.5.6 BLANK Card
- A.5.7 FMEC-E1 Specifications
- A.5.8 FMEC-DS1/E1 Card Specifications
- A.5.9 FMEC E1-120NP Card Specifications
- A.5.10 FMEC E1-120PROA Card Specifications
- A.5.11 FMEC E1-120PROB Card Specifications
- A.5.12 E1-75/120 Impedance Conversion Panel Specifications
- A.5.13 FMEC-E3/DS3 Card Specifications
- A.5.14 FMEC STM1E 1:1 Card Specifications
- A.5.15 FMEC-BLANK Card Specifications
- A.5.16 MIC-A/P Card Specifications
- A.5.17 MIC-C/T/P Card Specifications
- A.6 Optical Card Specifications
- A.6.1 OC3 IR 4/STM1 SH 1310 Card Specifications
- A.6.2 OC3 IR/STM1 SH 1310-8 Card Specifications
- A.6.3 OC12 IR/STM4 SH 1310 Card Specifications
- A.6.4 OC12 LR/STM4 LH 1310 Card Specifications
- A.6.5 OC12 LR/STM4 LH 1550 Card Specifications
- A.6.6 OC12 IR/STM4 SH 1310-4 Card Specifications
- A.6.7 OC48 IR/STM16 SH AS 1310 Card Specifications
- A.6.8 OC48 LR/STM16 LH AS 1550 Card Specifications
- A.6.9 OC48 ELR/STM16 EH 100 GHz Card Specifications
- A.6.10 OC192 SR/STM64 IO 1310 Card Specifications
- A.6.11 OC192 IR/STM64 SH 1550 Card Specifications
- A.6.12 OC192 LR/STM64 LH 1550 Card Specifications
- A.6.13 OC192 LR/STM64 LH ITU 15xx.xx Card Specifications
- A.7 Ethernet Card Specifications
- A.8 Storage Access Networking Card Specifications
- Administrative and Service States
- Network Element Defaults
- Index

9-8
Cisco ONS 15454 SDH Reference Manual, R5.0
April 2008
Chapter 9 Security and Timing
9.2.2 Synchronization Status Messaging
Figure 9-1 ONS 15454 SDH Timing Example
9.2.2 Synchronization Status Messaging
Synchronization status messaging (SSM) is an SDH protocol that communicates information about the
quality of the timing source. SSM messages are carried on the S1 byte of the SDH section overhead. They
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 9-5 shows the SDH message set.
Node 4
Timing Line
Ref 1: Slot 6
Ref 2: Slot 5
Ref 3: Internal (ST3)
Node 2
Timing Line
Ref 1: Slot 5
Ref 2: Slot 6
Ref 3: Internal (ST3)
Node 1
Timing External
Ref 1: BITS1
Ref 2: BITS2
Ref 3: Internal (ST3)
Node 3
Timing Line
Ref 1: Slot 5
Ref 2: Slot 6
Ref 3: Internal (ST3)
BITS1
out
BITS2
out
BITS1
source
BITS2
source
Third party
equipment
34726
Slot 5
Slot 5
Slot 5
Slot 5
Slot 6
Slot 6
Slot 6
Slot 6
Table 9-5 SDH SSM Message Set
Message Quality Description
G811 1 Primary reference clock
STU 2 Sync traceability unknown
G812T 3 Transit node clock traceable