1     Scope
 2     Functional aspects
        2.1     Dial-in and dial-out considerations
        2.2     Identification
        2.3     Service aspects
        2.4     DTE identification methods
        2.5     DCE identification methods
        2.6     Dial-in-by-the-DTE and dial-out-by-the-PSPDN operation
        2.7     DTE service requirement
        2.8     Duplex and half-duplex operation
        2.9     Identification protocol
       2.10     Negotiation of values
 3     DTE service descriptions
        3.1     DTE service attributes
        3.2     Summary of DTE services
        3.3     Non-identified DTE service
        3.4     Identified DTE service
        3.5     Customized DTE service
 4     Interface characteristics (physical layer)
        4.1     X.21 interface
        4.2     X.21 bis interface
        4.3     V-Series interface
 5     Link access procedure across the DTE/DCE interface
        5.1     Introduction
        5.2     Data link layer address assignment
        5.3     Use of exchange identification (XID) frames
        5.4     Link set-up disconnection
        5.5     Multilink
        5.6     Half-duplex operation
 6     Packet layer
        6.1     Scope and field of application
        6.2     Identification and authentication of the DTE using the NUI selection facility in call set‑up packets
 7     X.32 procedures, formats and facilities
        7.1     Identification protocol
        7.2     Procedures for X.32 optional user facilities
        7.3     Coding of the identification protocol elements
        7.4     Security grade 2 method
        7.5     DCE timers T14 and T14 bis
        7.6     DCE timer T15
Annex A – Actions taken by the DCE in the roles of questioning and challenged parties  for security grade 1 and security grade 2 identifications
        A.1     Introduction
        A.2     Security grade 1 identification
        A.3     Security grade 2 identification
Annex B – Abbreviations
Appendix I – Implementation of LAPX
        I.1     Introduction
        I.2     Control and status functions
        I.3     Table of transitions between states
        I.4     HDTM/physical layer control and status functions expressed in terms applicable to a modem interface
Appendix II – RSA public key algorithm
Appendix III – Relationship of timers T14 and T14 bis to the different methods of DTE identification