Rec. ITU-T V.42 (03/1993) ERROR-CORRECTING PROCEDURES FOR DCEs USING ASYNCHRONOUS-TO-SYNCHRONOUS CONVERSION
FOREWORD
CONTENTS
1 Scope
    1.1 General
    1.2 Relationship to other international standards
2 Definitions
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
    7.9 Operation of the DTE-DCE interface after failure to establish error-correcting operation
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
    9.3 Other parameters
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
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 Additional information for V.42 implementers regarding robustness of operation
III.1 Transmission of the answerer detection pattern
III.2 Value of parameter N400 (maximum number of retransmissions)
III.3 Incomplete XID exchange
III.4 Selective retransmission
III.5 Reject on detection of errored frames
III.6 Checkpointing
Appendix IV Factors for determining the acknowledgement 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
References