• CCITT Rec. Q.931 (11/1988) – ISDN USER-NETWORK INTERFACE LAYER 3 SPECIFICATION FOR BASIC CALL CONTROL
  • 1 General
    • 1.1 Scope of the Recommendation
    • 1.2 Application to interface structures
  • 2 Overview of call control
    • 2.1 Circuit switched calls
    • 2.2 Packet-mode access connections
    • 2.3 Temporary signalling connections
    • 2.4 States associated with the global call reference
  • 3 Message functional definitions and content
    • 3.1 Messages for circuit mode connection control
    • 3.2 Messages for packet-mode access connection control
    • 3.3 Messages for user-to-user signalling not associated with circuit switched calls
    • 3.4 Messages used with the global call reference
  • 4 General message format and information elements coding
    • 4.1 Overview
    • 4.2 Protocol discriminator
    • 4.3 Call reference
    • 4.4 Message type
    • 4.5 Other information elements
    • 4.6 Supplementary services information elements
    • 4.7 Information elements for packet communications
  • 5 Circuit-switched call control procedures
    • 5.1 Call establishment at the originating interface
    • 5.2 Call establishment at the destination interface
    • 5.3 Call clearing
    • 5.4 In-band tones and announcements
    • 5.5 Restart procedure
    • 5.6 Call rearrangements
    • 5.7 Call collisions
    • 5.8 Handling of error conditions
    • 5.9 User notification procedure
  • 6 Packet communications procedures
    • 6.1 Outgoing access
    • 6.2 Incoming access
    • 6.3 Virtual call establishment and release
    • 6.4 Call clearing
    • 6.5 Access collision
  • 7 User-to-user signalling procedures
    • 7.1 Procedures for user-to-user signalling associated with circuit-switched calls
    • 7.2 Procedures for user-to-user signalling not associated with circuit-switched calls
  • 8 Application of circuit-switched supplementary services to terminals using stimulus procedures
  • 9 List of system parameters
    • 9.1 Timers in the network side
    • 9.2 Timers in the user side
  • ANNEX A (to Recommendation Q.931) User side and network side SDL diagrams
  • ANNEX B (to Recommendation Q.931) Compatibility checking
    • B.1 Introduction
    • B.2 Calling side compatibility checking
    • B.3 Called side compatibility checking
    • B.4 Interworking with existing networks
  • ANNEX C (to Recommendation Q.931) Transit network selection
    • C.1 Selection not supported
    • C.2 Selection supported
  • ANNEX D (to Recommendation Q.931) Extensions for symmetric call operation
    • D.1 Additional message handling
    • D.2 Timers for call establishment
    • D.3 Call collisions
  • ANNEX E (to Recommendation Q.931) Network specific facility selection
    • E.1 Default provider
    • E.2 Routing not supported
    • E.3 Routing supported
  • ANNEX F (to Recommendation Q.931) D-channel backup procedures
    • F.0 Foreword
    • F.1 General
    • F.2 D-channel backup procedure
  • ANNEX G (to Recommendation Q.931) Cause definitions
    • G.1 Normal class
    • G.2 Resource unavailable class
    • G.3 Service or option not available class
    • G.4 Service or option not implemented class
    • G.5 Invalid message (e.g., parameter out of range) class
    • G.6 Protocol error (e.g., unknown message) class
    • G.7 Interworking class
  • ANNEX H (to Recommendation Q.931) Examples of information elements coding
    • H.1 Bearer capability information element
    • H.2 Channel identification information element
    • H.3 Called/calling party sub-address information element
  • ANNEX I (to Recommendation Q.931) Use of progress indicators
  • ANNEX J (to Recommendation Q.931) Examples of cause value and location for busy condition
  • ANNEX K (to Recommendation Q.931) Message segmentation procedures
    • K.1 Introduction
    • K.2 Message segmentation
    • K.3 Reassembly of segmented messages
  • ANNEX L (to Recommendation Q.931) Llow layer information coding principles
    • L.1 Purpose
    • L.2 Principles
    • L.3 Information classification
    • L.4 Scenarios outside the scope of ISDN standardization
  • ANNEX M (to Recommendation Q.931) Low layer compatibility negotiation
    • M.1 General
    • M.2 Low layer compatibility notification to the called user
    • M.3 Low layer compatibility negotiation between users
    • M.4 Low layer compatibility negotiation options
  • ANNEX N (to Recommendation Q.931) Procedures for establishment of bearer connection prior to call acceptance
    • N.1 General
    • N.2 Procedures
  • ANNEX O (to Recommendation Q.931) Optional procedures for bearer service change
  • APPENDIX I (to Recommendation Q.931) Usage of cause values
  • APPENDIX II (to Recommendation Q.931) Example message flow diagrams and example conditions for cause mapping
    • II.1 Example message flow diagrams
    • II.2 Example conditions for cause mapping
  • APPENDIX III (to Recommendation Q.931) Summary of assigned information element identifier and message type code p...
  • ACRONYMS USED IN RECOMMENDATION Q.931
  • References