ISO/IEC 21409:2001 PDF

Overview

ISO/IEC 21409:2001 defines signalling interworking between QSIG and H.323 to support the generic functional procedures for supplementary services in a Corporate Telecommunication Network (CN). It specifies how a gateway (interworking unit) maps and transports supplementary-service control information between a Private Integrated Services Network (PISN) using QSIG and an IP-based network using H.323 (including H.225.0, H.245 and H.450.1). The standard enables calls and supplementary-service control information to traverse from circuit-switched PISNs to packet (IP) networks and vice versa.

Key topics and technical requirements

• Scope and applicability
  • Applies to any gateway that interworks a PISN (QSIG at the Q reference point) and an IP network (H.323).
• Protocol interworking
  • Defines message and information-element mapping between QSIG and H.323/H.450.1.
  • Covers content mapping both directions (QSIG → H.323, H.323 → QSIG).
• Generic functional protocol (QSIG-GF / H.450.1)
  • Aligns QSIG’s Generic Functional protocol (ISO/IEC 11582) with H.450.1 generic procedures.
  • Describes transport of ROSE APDUs and handling of remote operations.
• Addressing and information elements
  • Mapping rules for addressing elements, embedded information elements, names, and manufacturer‑specific containers.
• Encoding and transport
  • Notes on ASN.1 encoding rules used (BER, PER variants) and use of IP transport (TCP/UDP) for H.323 signalling.
• Conformance
  • Gateways must meet requirements set out in the Implementation Conformance Statement (ICS) proforma (Annex A).
• Normative references
  • Related normative documents include ISO/IEC 11572, ISO/IEC 11579-1, ISO/IEC 11582, ITU-T H.225.0, H.245, H.323 and H.450.1.

Applications and who should use it

• Network architects and engineers designing CNs that combine legacy PISN/PBX systems and IP telephony.
• Gateway and PBX vendors who implement interworking between QSIG-based private exchanges (PINX) and H.323 endpoints or intranets.
• Systems integrators migrating voice/multimedia services from circuit-switched to packet networks while retaining supplementary services (call forwarding, hold, name display, etc.).
• Standards and compliance teams verifying interworking behavior and completing the ICS for product certification.

Related standards

• ISO/IEC 11572 (QSIG call control)
• ISO/IEC 11582 (QSIG Generic Functional protocol)
• ISO/IEC 11579-1 (PINX reference)
• ITU‑T H.323, H.225.0, H.245 (H.323 umbrella)
• ITU‑T H.450.1 (H.323 generic functional protocol)

ISO/IEC 21409 is a pragmatic, implementation-focused standard for interoperability between traditional PBX signalling (QSIG) and packet-based H.323 environments, ensuring consistent support for supplementary services across heterogeneous corporate networks.