Table of Contents

 1     Scope        
 2     References             
 3     Definitions
        3.1     Terms defined elsewhere      
        3.2     Terms defined in this Recommendation          
 4     Abbreviations and acronyms           
 5     Conventions           
        5.1     Representation of octets        
 6     Introduction           
 7     Network objectives
 8     Protection characteristics   
        8.1     Monitoring methods and conditions   
 9     Protection group commands           
        9.1     End-to-end commands and states       
        9.2     Local commands       
10     Protection architectures    
       10.1     Unidirectional and bidirectional switching     
       10.2     Need for APS communication            
       10.3     Revertive and non-revertive switching           
       10.4     Provisioning mismatches      
       10.5     Protection switching trigger 
       10.6     Protection switching models 
11     APS protocol         
       11.1     APS format  
       11.2     1-phase APS protocol            
       11.3     Request type            
       11.4     Protection types and bridge type       
       11.5     Requested signal      
       11.6     Bridged signal          
       11.7     Control of bridge     
       11.8     Control of selector   
       11.9     Signal fail of the protection transport entity  
      11.10     Equal priority requests         
      11.11     Command acceptance and retention             
      11.12     Hold-off timer         
      11.13     Wait-to-restore timer          
      11.14     Exercise operation  
      11.15     Failure of protocol defects   
      11.16     Signal degrade of the protection transport entity      
Annex A – State transition tables of protection switching    
        A.1     State transition for 1:1 bidirectional switching with revertive mode     
        A.2     State transition for 1:1 bidirectional switching with non-revertive mode           
        A.3     State transition for 1+1 bidirectional switching with revertive mode    
        A.4     State transition for 1+1 bidirectional switching with non-revertive mode          
        A.5     State transition for 1+1 unidirectional switching with revertive mode  
        A.6     State transition for 1+1 unidirectional switching with non-revertive mode        
Appendix I – Example of operation of 1-phase APS protocol    
        I.1     Introduction  
        I.2     Example scenario      
        I.3     Examples of APS protocol       
Appendix II – Interaction between Ethernet protection switching and spanning-tree protocol (STP)    
Appendix III – Maintenance entity group intermediate points for a protection switching environment    
      III.1     Introduction  
      III.2     Considerations           
      III.3     Examples of configuration      
Appendix IV – State transition diagrams using specification and description language    
       IV.1     Introduction 
       IV.2     SDL diagrams