Overview
ISO/IEC 14842:1996 specifies the Do Not Disturb (SS‑DND) and Do Not Disturb Override (SS‑DNDO) supplementary services for Private Integrated Services Networks (PISN). This International Standard provides the stage 1 (service definitions for users) and stage 2 (functional model and information flows) specifications that define behavior, functional entities, and signalling relationships required to support DND and DNDO in PISN environments. Stage 3 (detailed signalling protocols and equipment behaviour) is required to claim full conformance.
Key topics and technical requirements
- Service definitions: SS‑DND enables a served user’s PISN number to reject incoming calls (optionally per basic service); SS‑DNDO enables a calling user to override an active DND subject to service profiles.
- Specification stages: Contains stage 1 (user view) and stage 2 (functional entities, information flows, state machines). Stage 3 must specify signalling protocols that implement these stages.
- Functional model: Identifies functional entities (FE1…FE6 in the stage‑2 model), their actions and behaviours, allocation to physical equipment and inter‑FE information flows.
- Subscription parameters: Includes options such as DND Protection Level (DNDPL) with values 0–3 (0 = no protection; 3 = total protection; 0 and 3 must be offered; 1 and 2 optional). Also defines other subscription/profile options (e.g., per‑basic‑service subscription).
- Procedures: Covers provision/withdrawal, normal and exceptional procedures, timers (e.g., consultation timer), and path retention to enable DNDO invocation without re‑establishing connections.
- Interactions and interworking: Specifies interactions with many supplementary services and network features (for example SS‑CLIP, SS‑COLP, SS‑CLIR, SS‑CNIP, SS‑CT, SS‑CFU, SS‑CFB, SS‑CD, ANF‑PR, SS‑CO, SS‑CI) and includes interworking considerations with other PISN standards.
- Scope of applicability: Applicable to circuit‑mode basic services defined in ISO/IEC 11574.
Applications and who uses this standard
- Telecom equipment vendors (PBX / PINX / PISN manufacturers) implementing DND/DNDO features.
- Network architects and operators designing service profiles and subscriber options in enterprise telephony.
- Standards bodies and protocol designers producing stage‑3 signalling specifications.
- System integrators and telecom software developers implementing call control, service logic, and interoperability with other supplementary services.
Practical uses include implementing per‑number DND for enterprise users, controlled override for priority callers, and ensuring correct interactions with caller‑ID, call forwarding, call transfer and call completion features.
Related standards
Keywords: ISO/IEC 14842:1996, Do Not Disturb, DND, Do Not Disturb Override, DNDO, PISN, supplementary service, stage 1, stage 2, functional model, information flows, DND protection level.