ISO/IEC 13873:2003 PDF

Overview

ISO/IEC 13873:2003 defines the signalling protocol used at the Q reference point between Private Integrated services Network eXchanges (PINXs) to support Call Diversion supplementary services in a Private Integrated Services Network (PISN). This stage‑3 specification (part of the PSS1 / QSIG family) covers Call Forwarding Unconditional (SS‑CFU), Call Forwarding Busy (SS‑CFB), Call Forwarding No Reply (SS‑CFNR) and Call Deflection (SS‑CD). The standard describes how PINXs interoperate to forward or deflect incoming calls, how diversion reasons are signalled, and how interactions with other supplementary services and Additional Network Features (ANFs) are handled.

Key Topics and Requirements

• Scope and conformance: Applicable to PINXs interconnected into a PISN; conformance is verified using the Protocol Implementation Conformance Statement (PICS) proforma (Annex A).
• Stage‑3 signalling protocol: Detailed message formats, operations and information elements for SS‑DIV at the Q reference point (uses ASN.1, SDL representations and message sequence examples in annexes).
• Operational requirements: Roles and requirements for Originating, Served‑user, Diverted‑to, Rerouting, Transit, Activating, Deactivating and Interrogating PINXs.
• Protocol layering: SS‑DIV operates on top of the basic circuit‑switched call control signalling (ISO/IEC 11572) and leverages generic supplementary service procedures (ISO/IEC 11582).
• Interactions and interworking: Procedures addressing interactions with other supplementary services and the impact of interworking with public ISDNs and non‑ISDN networks.
• State machines and procedures: State definitions for involved PINXs and detailed signalling procedures for call diversion, forward switching, rerouting and partial rerouting.
• Timers and parameters: Protocol timers (T1–T5) and parameterisation for reliable operation (values and usage specified without prescribing network operator settings).
• Implementation artifacts: Imported ASN.1 definitions, SDL procedure models and example message sequences to aid implementers.

Practical Applications and Users

ISO/IEC 13873:2003 is primarily used by:

• PBX and PBX‑vendor engineers implementing QSIG call diversion features across multi‑site enterprise networks.
• Telecommunications integrators and system architects designing PISN interconnectivity and call routing policies.
• Test houses and QA teams using the PICS proforma and message examples for interoperability testing between PINXs.
• Network operators ensuring correct interworking with public ISDN gateways and legacy networks for consistent call‑forwarding behavior. Practical benefits include consistent cross‑vendor support for call forwarding/deflection, predictable user experience across sites, and reduced configuration complexity for multi‑site enterprises.

Related Standards

• ISO/IEC 11579‑1 (PISN reference configuration)
• ISO/IEC 11572 (circuit switched call control signalling)
• ISO/IEC 11582 (generic supplementary service protocol)
• ISO/IEC 13872 (stage 1/2 specification for Call Diversion)
• Other QSIG family standards (ISO/IEC 13868, 13869, 13870)
• ETS 300 387 and ITU‑T Q‑series recommendations (Q.950/Q.952)

Keywords: ISO/IEC 13873:2003, QSIG, Call Diversion, Call Forwarding Unconditional, Call Forwarding Busy, Call Forwarding No Reply, Call Deflection, PISN, PINX, Q reference point, signalling protocol.