1              Scope                   

2              References                        

3              Terms and definitions                   

4              Abbreviations and acronyms                      

5              Synchronization principles                           

5.1          Network synchronization                            

5.2          Synchronization distribution trails            

5.3          Synchronization interfaces                          

5.4          Clock-source quality-level                           

5.5          Synchronization status messages (SSMs), extended QL TLV, and timing marker (TM) channels                      

5.6          Selection process            

5.7          Signal fail                            

5.8          Hold-off time                    

5.9          Wait-to-restore time                     

5.10        Synchronization source priorities                              

5.11        External commands                       

5.12        Automatic reference selection process                  

5.13        Timing loop prevention                

5.14        Delay times for NEs with SEC/ST3/SIC                     

5.15        Delay times for NEs with SSU/ST2 or for SASE/BITS                           

5.16        Synchronization layer functions                

5.17        Overview of the processes performed within the atomic functions                            

5.18        Interworking between option I, II and III synchronization networks                           

6              Synchronization distribution layer atomic functions                         

6.1          SD connection function (SD_C)  

6.2          SD trail termination functions    

6.3          SD adaptation functions               

7              Network synchronization layer atomic functions               

7.1          NS_connection functions (NS_C)                              

8              Transport layer to SD layer atomic functions                       

8.1          STM‑n multiplex section adaptation functions                    

8.2          Pqs adaptation functions                             

8.3          P12s layer adaptation functions                

8.4          T12 layer adaptation functions                  

8.5          P11s layer adaptation functions                

8.6          T01 layer adaptation functions                  

8.7          T02 layer adaptation functions                  

8.8          T21 layer adaptation functions                  

8.9          ETH layer adaptation functions                 

8.10        OTUk layer adaptation functions              

8.11        OSC layer adaptation functions                 

8.12        FlexO layer adaptation functions                              

9              Equipment clock to transport layers clock adaptation functions                  

9.1          STM-N layer                       89

9.2          VC layers                             

9.3          Pxx layers                           

9.4          T12 layer                             

9.5          T01 layer                             

9.6          T02 layer                             

9.7          T21 layer                             

9.8          ETYn layer                          

9.9          ODU layer                           

9.10        OSC layer                            

9.11        FlexO layer                         

10           T12 section layer functions                         

10.1        T12 connection function T12_C                 

10.2        T12 trail termination functions                  

11           T01 section layer functions                         

11.1        T01 connection function T01_C                 

11.2        T01 trail termination functions                  

12           T02 section layer functions                         

12.1        T02 connection function T02_C                 

12.2        T02 trail termination functions                  

13           T21 section layer functions                         

13.1        T21 connection function T21_C                 

13.2        T21 trail termination functions                  

Annex A – Synchronization selection process                      

Appendix I – Transport layer models for synchronization information                      

Appendix II – Examples of synchronization functionality in the NE                              

II.1          Examples of synchronization functionality in the NE for option I networks                             

II.2          Examples of synchronization functionality in the NE for option II networks                            

II.3          Examples of synchronization functionality in the NE for option III networks                           

Appendix III – Delay time allocation for option I and III networks               

III.1        Delay and processing times for the synchronization selection process                      

III.2        Non‑switching message delay TNSM                      

III.3        Switching message delay TSM                   

III.4        Holdover message delay THM                    

III.5        Wait-to-restore time TWTR                         

Appendix IV – Interworking of option II equipment supporting second-generation SSM  and first-generation SSM using a translation function    

Appendix V – SDL descriptions                   

Appendix VI – Clarification of the use of the acronym 'SEC'                            

Appendix VII – Use cases of mixing SSM and eSSM