Overview
ISO/IEC 13866:1995 - Information technology - Telecommunications and information exchange between systems - Private Integrated Services Network (PISN) - Specification, functional model and information flows - Call completion supplementary services - defines the Call Completion (SS-CC) supplementary services for PISNs. The standard is part of a series that uses ISDN concepts (ITU‑T) and the OSI framework (ISO/IEC). It specifies two SS-CC services: Completion of Calls to Busy Subscribers (SS-CCBS) and Completion of Calls on No Reply (SS-CCNR), and provides Stage 1 (user/service view) and Stage 2 (functional model and information flows) descriptions.
Key topics and requirements
- Scope and purpose: Defines user-visible behaviour and network functional entities required to support call completion features in Private Integrated Services Networks.
- Service types: SS-CCBS (notify when a busy called party becomes free) and SS-CCNR (notify when alerted party does not answer).
- Stage-based specification:
- Stage 1 - user-oriented service descriptions, procedures for provisioning, activation, invocation, cancellation and exceptional handling.
- Stage 2 - functional model, allocation of Functional Entities (FE1–FE4) (originating/terminating agents and controllers), and detailed information flows between entities.
- Information flows and signalling: Defines message flows (e.g., ra-CC-request, rb-CC-call, cancel/notification flows) and examples of invocation, reservation, completion and failure sequences.
- Timers and features: Introduces concepts such as recall timer, retention timer, path reservation and SS-CC service duration timer (behavioural roles, not fixed values).
- Interactions: Specifies interactions with other supplementary services (SS-CLIP, SS-COLP, SS-CFU, SS-CFB, SS-CFNR, call transfer, etc.) and interworking considerations.
- Conformance: To claim conformance a Stage 3 specification must define signalling protocols and equipment behaviour adequate to support the Stage 1/2 clauses relevant to the interface or equipment.
Applications and who uses it
- Telecommunications standards engineers and protocol designers implementing PISN services.
- PBX and PISN equipment manufacturers who need to implement call completion supplementary services.
- Network architects and system integrators deploying ISDN/PISN features inside enterprises.
- Test labs creating interoperability tests for SS-CC behaviour and interworking with supplementary services.
Practical benefits include improved call handling automation (auto-recall when busy/ no-reply), consistent user experience across PISN equipment, and a clear functional basis for signalling protocol implementation.
Related standards
- ISO/IEC 11574 - PISN basic call service definitions and functional entities
- ISO/IEC 11579‑1 - Reference configuration for PISN Exchanges (PINX)
- ITU‑T Recommendations referenced (e.g., Rec. 1.130, Rec. 1.210) for service characterization and terminology
Keywords: ISO/IEC 13866:1995, PISN, Call Completion, SS-CC, SS-CCBS, SS-CCNR, ISDN, functional model, information flows, recall timer, path reservation.
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