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• 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