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• CCITT Rec. Q.87.1 (1988) – ADDITIONAL INFORMATION TRANSFER SUPPLEMENTARY SERVICES – ISDN USER-TO-USER SIGNALLING SERVICES
• 1 ISDN user-to-user signalling services
  • 1.1 General
  • 1.2 Description of service uses
    • 1.1.1 General description
    • 1.2.2 Signalling information transfer
    • 1.2.3 Service invocation
  • 1.3 Derivation of the functional model for user-to-user signalling
    • 1.3.1 Functional model
  • 1.4 Information flow diagrams
  • 1.5 SLD diagrams for functional entities
    • 1.5.1 SLDs for FE1 and FE5
    • 1.5.2 Stage 2 SDLs for FE2 fiCC functional entity (r1-r1)fl
    • 1.5.3 SLDs for functional entity FE3
    • 1.5.4 SDL for functional entity FE4
  • 1.6 Functional entity actions
    • 1.6.1 Check UUS service request
    • 1.6.2 Check for UUI to END user
    • 1.6.3 Check called user response
    • 1.6.4 Check which services are available to calling user
    • 1.6.5 Is UUI or UUM transfer allowed?
    • 1.6.6 Check limit of Service 2 UUMs
    • 1.6.7 Can a UUI compatible path be found?
  • 1.7 Allocation of functional entities to physical location