1     Scope        
 2     References             
 3     Definitions
 4     Symbols and abbreviations 
 5     Conventions           
 6     System description
        6.1     Information streams 
        6.2     Terminal characteristics        
        6.3     Gateway characteristics        
        6.4     Gatekeeper characteristics    
        6.5     Multipoint controller characteristics  
        6.6     Multipoint processor characteristics  
        6.7     Multipoint control unit characteristics            
        6.8     Multipoint capability
        6.9     Models for supplementary services    
 7     Call signalling        
        7.1     Addresses     
        7.2     Registration, Admission and Status (RAS) channel        
        7.3     Call signalling channel           
        7.4     Call reference value 
        7.5     Call ID          
        7.6     Conference ID and conference goal   
        7.7     Endpoint call capacity            
        7.8     Caller identification services 
        7.9     Generic extensible framework           
 8     Call signalling procedures  
        8.1     Phase A – Call setup 
        8.2     Phase B – Initial communication and capability exchange        
        8.3     Phase C – Establishment of audiovisual communication           
        8.4     Phase D – Call services          
        8.5     Phase E – Call termination    
        8.6     Protocol failure handling       
 9     Interoperation with other terminal types     
        9.1     Speech-only terminals           
        9.2     Visual telephone terminals over the ISDN (Rec. ITU-T H.320)   
        9.3     Visual telephone terminals over GSTN (Rec. ITU-T H.324)        
        9.4     Visual telephone terminals over mobile radio (Annex C/H.324, a.k.a. "H.324/M")          
        9.5     Visual telephone terminals over ATM (H.321 and H.310 RAST)
        9.6     Visual telephone terminals over guaranteed quality of service LANs (Rec. ITU‑T H.322)    
        9.7     Simultaneous voice and data terminals over GSTN (Rec. ITU-T V.70)    
        9.8     T.120 terminals on the packet-based network
        9.9     Gateway for H.323 media transport over ATM            
10     Optional enhancements    
       10.1     Encryption   
       10.2     Multipoint operation             
       10.3     Call Linkage in H.323            
       10.4     Tunnelling of non-H.323 signalling messages 
       10.5     Use of RTP payload for DTMF digits, telephony tones and telephony signals     
11     Maintenance        
       11.1     Loopbacks for maintenance purposes             
       11.2     Monitoring methods
Annex A – H.245 messages used by H.323 endpoints    
Annex B – Procedures for layered video codecs    
        B.1     Scope           
        B.2     Introduction 
        B.3     Scalability methods  
        B.4     Call establishment    
        B.5     Use of RTP sessions and codec layers 
        B.6     Possible layering models       
        B.7     Impact on multipoint conferences      
        B.8     Use of network QoS for layered video streams            
Annex C – H.323 on ATM    
        C.1     Introduction 
        C.2     Scope           
        C.3     Architecture
        C.4     Protocol section        
Annex D – Real-time facsimile over H.323 systems    
        D.1     Introduction 
        D.2     Scope           
        D.3     Procedures for opening channels to send T.38 packets             
        D.4     Non-fast connect procedures
        D.5     Replacing an existing audio stream with a T.38 fax stream     
        D.6     Usage of the maxBitRate/bandWidth in messages      
        D.7     Interactions with gateways and T.38/Annex B devices
Annex E – Framework and wire‑protocol for multiplexed call signalling transport    
        E.1     Scope           
        E.2     H.225.0 call signalling over UDP         
Annex F – Simple endpoint types    
        F.1     Introduction 
        F.2     Specification conventions       
        F.3     Scope            
        F.4     Normative references            
        F.5     Abbreviations            
        F.6     Simple (Audio) Endpoint Type – System functionality overview
        F.7     Procedures for Simple Endpoint Types             
        F.8     Security extensions   
        F.9     Interoperability considerations           
       F.10     Implementation notes (Informative)  
Annex G – Text conversation and Text SET    
        G.1     Introduction 
        G.2     Scope           
        G.3     References  
        G.4     Definitions   
        G.5     Capability Advertisement for Text in H.323    
        G.6     Procedures for opening channels for T.140 text conversation  
        G.7     Framing and buffering of T.140 data 
        G.8     Interaction with text conversation facilities in other devices    
        G.9     Multipoint considerations     
       G.10     Text SET: Text Conversation Simple Endpoint Type     
Annex J – Security for Annex F    
        J.1              Introduction      
        J.2              Specification conventions           
        J.3              Scope   
        J.4              Abbreviations   
        J.5              Normative references   
        J.6              Secure Audio Simple Endpoint Type (SASET)        
Annex K – HTTP‑based service control transport channel    
        K.1     Introduction 
        K.2     Service control in H.323         
        K.3     Usage of HTTP          
        K.4     Example scenarios    
        K.5     References   
Annex L – Stimulus control protocol    
        L.1     Scope            
        L.2     Introduction 
        L.3     Stimulus framework  
        L.4     References   
Annex M1 – Tunnelling of signalling protocols (QSIG) in H.323    
       M1.1     Scope         
       M1.2     Normative references         
       M1.3     Endpoint procedures           
       M1.4     Tunnelling of QSIG connection-oriented call-independent signalling  
       M1.5     Gatekeeper procedures       
Annex M2 – Tunnelling of signalling protocols (ISUP) in H.323    
       M2.1     Scope         
       M2.2     Normative references         
       M2.3     Endpoint procedures           
       M2.4     Gatekeeper procedures       
Annex M3 – Tunnelling of DSS1 through H.323    
       M3.1     Scope         
       M3.2     Normative references         
       M3.3     Endpoint procedures           
       M3.4     Tunnelling of bearer-independent DSS1 signalling    
       M3.5     Gatekeeper procedures       
Annex M4 – Tunnelling of narrow‑band signalling syntax (NSS) for H.323    
       M4.1     Scope         
       M4.2     References
       M4.3     H.225.0 Endpoint procedures           
       M4.4     Gatekeeper procedures       
       M4.5     RAS procedures for direct-routed calls         
Annex M5 – Tunnelling of common alerting protocol (CAP) messages in H.323    
       M5.1     Scope         
       M5.2     Normative references         
       M5.3     Identifying CAP messages   
       M5.4     Signalling support for CAP   
       M5.5     Transporting CAP within H.225.0 messages  
       M5.6     Transmitting and processing CAP messages 
       M5.7     Requesting CAP support when initiating calls            
       M5.8     Gatekeeper procedures       
Annex O – Usage of URLs and DNS    
        O.1     Scope           
        O.2     Normative references           
        O.3     Informative references         
        O.4     H.323 URL   
        O.5     Encoding of H.323 URL in H.323 messages     
        O.6     Non-H.323 URLs and URIs within the context of H.323
        O.7     H.323 URL parameters          
        O.8     Usage of the H.323 URL        
        O.9     Resolving an H.323 URL to IP Address using DNS         
       O.10     Using DNS SRV Resource Records     
Annex P – Transfer of modem signals over H.323    
        P.1     Scope           
        P.2     References   
        P.3     Definitions   
        P.4     Abbreviations            
        P.5     Introduction 
        P.6     Capability advertisement       
        P.7     Call establishment    
        P.8     Logical channel signalling      
Annex Q – Far-end camera control and H.281/H.224    
        Q.1     Scope           
        Q.2     References  
        Q.3     Introduction
        Q.4     Far-end camera control protocol       
        Q.5     RTP header information        
Annex R – Robustness methods for H.323 entities    
        R.1     Introduction and scope          
        R.2     Normative references           
        R.3     Definitions   
        R.4     Abbreviations            
        R.5     Overview of the two methods            
        R.6     Common mechanisms           
        R.7     Method A: State recovery from neighbours    
        R.8     Method B: State recovery from a shared repository    
        R.9     Interworking between robustness methods     
       R.10     Procedures for recovery       
       R.11     GenericData usage  
Appendix I – Sample MC to terminal communication mode command    
        I.1               Sample conference Scenario A   
        I.2               CommunicationModeTable sent to all endpoints 
        I.3               Sample conference Scenario B   
        I.4               CommunicationModeTable sent to all endpoints 
Appendix II – Transport level resource reservation procedures    
       II.1     Introduction  
       II.2     QoS support for H.323            
       II.3     RSVP background       
       II.4     The H.245 capability exchange phase 
       II.5     Open logical channel and setting up reservations         
       II.6     Close logical channel and tearing down reservations   
       II.7     Resource reservation for multicast H.323 logical channels        
       II.8     Synchronized RSVP     
Appendix III – Gatekeeper‑based user location    
      III.1     Introduction  
      III.2     Signalling      
Appendix IV – Signalling prioritized alternative logical channels in ITU-T H.245    
       IV.1     Introduction 
       IV.2     Signalling     
Appendix V – Use of ITU-T E.164 and ISO/IEC 11571 numbering plans    
        V.1     E.164 numbering plan           
        V.2     Private network number        
        V.3     H.323 versions 1, 2 and 3 usage         
Appendix VI – Description of a typical ITU-T H.323 system over IP    
Appendix VII – Informative notes on robustness methods for ITU-T H.323 entities    
      VII.1     Informative Note 1: Background on robustness methods          
      VII.2     Informative Note 2: Call state sharing between an entity and its backup peer