• CCITT Rec. X.2 (11/1988) – INTERNATIONAL DATA TRANSMISSION SERVICES AND OPTIONAL USER FACILITIES IN PUBLIC DATA NETWORKS AND ISDNs
  • 1 Circuit switched data transmission service
  • 2 Packet switched data transmission services
    • 2.1 Direct connection to a packet switched data transmission service
    • 2.2 Switched connection to a packet switched data transmission service (classes of service 20-23)
    • 2.3 Switched connection to a packet switched data transmission service (classes of service 8-13)
  • 3 Leased circuit data transmission services
  • APPENDIX I