• CCITT Rec. X.25 (11/1988) – INTERFACE BETWEEN DATA TERMINAL EQUIPMENT (DTE) AND DATA CIRCUIT-TERMINATING EQUIPMENT (DCE) FOR TERMINALS OPERATING...
  • CONTENTS
  • 1 DTE/DCE interface characteristics (physical layer)
    • 1.1 X.21 interface
    • 1.2 X.21 bis interface
    • 1.3 V-Series interface
    • 1.4 X.31 interface
  • 2 Link access procedures across the DTE/DCE interface
    • 2.1 Scope and field of applications
    • 2.2 Frame structure
    • 2.3 LAPB elements of procedures
    • 2.4 Description of the LAPB procedure
    • 2.5 Multilink procedure (MLP) (Subscription-time selectable option)
    • 2.6 LAP elements of procedure
    • 2.7 Description of the LAP procedure
  • 3 Description of the packet level DTE/DCE interface
    • 3.1 Logical channels
    • 3.2 Basic structure of packets
    • 3.3 Procedure for restart
    • 3.4 Error handling
  • 4 Procedures for virtual circuit services
    • 4.1 Procedures for virtual call service
    • 4.2 Procedures for permanent virtual circuit service
    • 4.3 Procedures for data and interrupt transfer
    • 4.4 Procedures for flow control
    • 4.5 Effects of clear, reset and restart procedures on the transfer of packets
    • 4.6 Effects of the physical layer and the data link layer on the packet layer
  • 5 Packet formats
    • 5.1 General
    • 5.2 Call set-up and clearing packets
    • 5.3 Data and interrupt packets
    • 5.4 Flow control and reset packets
    • 5.5 Restart packets
    • 5.6 Diagnostic packet
    • 5.7 Packets required for optional user facilities
  • 6 Procedures for optional user facilities (packet layer)
    • 6.1 On-line facility registration
    • 6.2 Extended packet sequence numbering
    • 6.3 D bit modification
    • 6.4 Packet retransmission
    • 6.5 Incoming calls barred
    • 6.6 Outgoing calls barred
    • 6.7 One-way logical channel outgoing
    • 6.8 One-way logical channel incoming
    • 6.9 Non-standard default packet sizes
    • 6.10 Non-standard default window sizes
    • 6.11 Default throughput classes assignment
    • 6.12 Flow control parameter negotiation
    • 6.13 Throughput class negotiation
    • 6.14 Closed user group related facilities
    • 6.15 Bilateral closed user group related facilities
    • 6.16 Fast select
    • 6.17 Fast select acceptance
    • 6.18 Reverse charging
    • 6.19 Reverse charging acceptance
    • 6.20 Local charging prevention
    • 6.21 Network user identification (NUI) related facilities
    • 6.22 Charging information
    • 6.23 RPOA related facilities
    • 6.24 Hunt group
    • 6.25 Call redirection and call deflection related facilities
    • 6.26 Called line address modified notification
    • 6.27 Transit delay selection and indication
    • 6.28 TOA/NPI address subscription
  • 7 Formats for facility fields and registration fields
    • 7.1 General
    • 7.2 Coding of facility field in call set-up and clearing packets
    • 7.3 Coding of the registration field of registration packets
  • ANNEX A – Range of logical channels used for virtual calls and permanent virtual circuits
  • ANNEX B – Packet layer DTE/DCE interface state diagrams
  • B.1 Symbol definition of the state diagrams
  • B.2 Order definition of the state diagrams
  • ANNEX C – Actions taken by the DCE on receipt of packets in a given state of the packet layer DTE/DCE interface as perceived ...
  • Introduction
  • ANNEX D – Packet layer DCE time-outs and DTE time-limits
  • D.1 DCE time-outs
  • D.2 DTE time-limits
  • ANNEX E – Coding of X.25 network generated diagnostic fields in clear, reset and restart indication, registration ...
  • ANNEX F – Applicability of the on-line facility registration facility to other facilities
  • ANNEX G – CCITT-specified DTE facilities to support the OSI Network service
  • G.1 Introduction
  • G.2 Coding of the facility code fields
  • G.3 Coding of the facility parameter field
  • ANNEX H – Subscription-time optional user facilities that may be associated with a network user identifier in conjunction ...
  • APPENDIX I – Examples of data link layer transmitted bit patterns by the DCE and the DTE
  • APPENDIX II – An explanation of how the values for N1 in Section 2.4.8.5 are derived
  • Introduction
  • APPENDIX III – Examples of multilink resetting procedures
  • III.1 Introduction
  • III.2 MLP reset initiated by either the DCE or the DTE
  • III.3 MLP reset initiated by both the DCE and the DTE simultaneously
  • APPENDIX IV – Information on addresses in call set-up and clearing packets
  • IV.1 Main address and complementary address
  • IV.2 Addresses in call request packet
  • IV.3 Addresses in incoming call packets
  • IV.4 Addresses in call accepted packets
  • IV.5 Addresses in call connected packets
  • IV.6 Addresses in clear request packets
  • IV.7 Addresses in clear indication packets
  • IV.8 Addresses in clear confirmation packets
  • IV.9 Addresses in call redirection and call deflection related facilities