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     Recommendation version      
        5.2     SDP Offer/Answer protocol variants   
 6     Definition of the VBD mode of operation     
        6.1     Minimum requirements for VBD mode of operation   
        6.2     Echo canceller and VBD mode            
        6.3     IP transport services for VBD 
 7     Negotiation of support of VBD and selection of VBD codec and other VBD enhanced functionality    
        7.1     Negotiation using the session description protocol      
        7.2     Use of VBD in ITU-T H.323 systems    
        7.3     Mid-call negotiation using session description protocol            
 8     The use of IETF RFC 4733 modem/facsimile/text telephone events   
 9     VBD stimuli            
10     Procedures for transitioning between audio mode and VBD mode   
       10.1     Procedures for state transitioning     
       10.2     State machine – Overview    
       10.3     Enforced state transition by call/session control         
11     Optional procedures for indicating to a remote end transition into VBD using state signalling events    
       11.1     Declaration of SSEs  
       11.2     Transition to the VBD mode for ITU‑T V.150.1 gateways         
       11.3     Transition to the VBD mode for non- ITU‑T V.150 cases           
       11.4     Transition from the VBD media mode            
       11.5     Security – Optional  
Annex A – Vendor-defined messages    
Annex B – Use of data signal detection and silence insertion in voiceband data    
        B.1     Introduction 
        B.2     Guideline for the use of DSD 
        B.3     Negotiation of the DSD capability with SDP    
        B.4     Negotiation of the DSD capability with [ITU‑T H.245]  
Annex C – Use of ITU‑T V.21 preamble for echo canceller control in an ITU‑T V.152 gateway