• CCITT Rec. V.42 (11/1988) – ERROR-CORRECTING PROCEDURES FOR DCES USING ASYNCHRONOUS-TO-SYNCHRONOUS CONVERSION
  • CONTENTS
  • 1 Scope
    • 1.1 General
    • 1.2 Relationship to other international standards
  • 2 Definitions
    • 2.1 DCE
    • 2.2 error-Correcting DCE
  • 3 Abbreviations
  • 4 Establishing an error-corrected connection
  • 5 Interchange circuits affected by error correction
  • 6 Overview of error-correcting DCE operation
    • 6.1 General
    • 6.2 Overview of the control function
    • 6.3 Overview of the error control function
    • 6.4 Communication between the control function and the error control function
  • 7 Operation of the control function
    • 7.1 Physical handshake
    • 7.2 Phases of error-correcting protocol establishment
    • 7.3 Data transfer
    • 7.4 Transfer of break signal
    • 7.5 Receipt of break
    • 7.6 Negotiation/indication of parameter values and optional procedures
    • 7.7 Orderly release of the error-corrected connection
    • 7.8 Loop-back test
  • 8 Operation of the error control function: LAPM procedures
    • 8.1 General
    • 8.2 LAPM elements of procedures and field formats
    • 8.3 Establishment of the error-corrected connection
    • 8.4 Transfer of user data from the V.24 interface
    • 8.5 Exception condition reporting and recovery
    • 8.6 Transfer of user-control information
    • 8.7 Orderly release of an error-corrected connection
    • 8.8 Disconnected state
    • 8.9 Collision of unnumbered commands and responses
    • 8.10 Negotiation/indication of parameter values and optional procedures
    • 8.11 Loop-back test
    • 8.12 Monitoring functions
    • 8.13 Transfer of break
  • 9 System parameters
    • 9.1 Parameters of the control function
    • 9.2 Parameters of the error control function
  • 10 Negotiation of optional procedures
  • 11 Control function-to-control function connection
  • 12 Encoding of information fields
    • 12.1 Information fields in I frames
    • 12.2 Information fields in XID frames
    • 12.3 Information fields in UI frames
    • 12.4 Information fields in TEST frame
  • References
  • ANNEX A – Operation of the error control function - Alternative procedure
  • A.1 General
  • A.2 Format conventions
  • A.3 Start-stop, octet-oriented framing mode
  • A.4 Bit-oriented framing mode
  • A.5 Invalid frames
  • A.6 Alternative elements of procedure and field formats
  • A.7 Description of the error-correcting procedure
  • ANNEX B – Mapping of character formats to 8-bit format
  • APPENDIX I – Interworking with a non-error correcting DCE
  • I.1 Interworking with a non-error-correcting answerer
  • I.2 Interworking with a non-error-correcting originator
  • I.3 Disposition of unrecognized bits
  • APPENDIX II – Data forwarding conditions
  • APPENDIX III – Cross-reference with CCITT Recommendations Q.920 and Q.921
  • APPENDIX IV – Factors for determining the acknowledgment timer
  • APPENDIX V – Potential enhancements to LAPM protocol
  • V.1 Data compression
  • V.2 Forward error correction
  • V.3 Statistical multiplexing
  • V.4 End-to-end transport of interface state information
  • V.5 Issues related to control function-to-control function information exchange
  • V.6 Rate negotiation
  • V.7 Operation over an asymmetric or half-duplex physical connection
  • V.8 Multiple frame reject
  • V.9 Character format indication/negotiation
  • V.10 Preservation of framing/parity errors
  • V.11 Encryption
  • V.12 ISDN compatibility