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 (ITU-T Rec. H.320) 
        9.3     Visual telephone terminals over GSTN (ITU-T Rec. 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 (ITU-T Rec. H.322)     
        9.7     Simultaneous voice and data terminals over GSTN (ITU-T Rec. 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.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.2     Scope    
        C.3     Architecture        
        C.4     Protocol section   
Annex D Real-time facsimile over H.323 systems     
        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.2     H.225.0 call signalling over Annex E      
Annex F Simple endpoint types     
        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.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.2     Service control in H.323 
        K.3     Usage of HTTP   
        K.4     Example scenarios           
        K.5     References          
Annex L Stimulus control protocol     
        L.2     Introduction        
        L.3     Stimulus framework        
        L.4     References           
Annex M1 Tunnelling of signalling protocols (QSIG) in H.323     
       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     
       M2.2     Normative references    
       M2.3     Endpoint procedures     
       M2.4     Gatekeeper procedures  
Annex M3 Tunnelling of DSS1 through H.323     
       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     
       M4.2     References         
       M4.3     H.225.0 Endpoint procedures   
       M4.4     Gatekeeper procedures  
       M4.5     RAS procedures for direct-routed calls
Annex O Usage of URLs and DNS     
        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.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.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     
     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         
       R.12     Informative Note 1: Background on robustness methods         
       R.13     Informative Note 2: Call state sharing between an entity and its backup peer 
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 H.245     
       IV.1     Introduction       
       IV.2     Signalling
Appendix V Use of 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 H.323 system over IP