ISO/IEC 21408:2003 PDF

Overview

ISO/IEC 21408:2003 specifies the signalling protocol for the Simple Dialog supplementary service (SS‑SD) at the Q reference point between Private Integrated services Network eXchanges (PINXs) within a Private Integrated Services Network (PISN). Often implemented as part of the QSIG family (PSS1), SS‑SD enables transparent exchange of display and keypad information between a Server User and a Client User over inter‑PINX links. ISO/IEC 21408:2003 is the stage‑3 protocol specification that fulfils stage‑1/2 requirements in ISO/IEC 21407.

Key topics and technical requirements

• Scope and conformance
  • Applies to PINXs that interconnect to form a PISN; conformance is verified via the PICS proforma (Annex A).
• Signalling protocol architecture
  • SS‑SD operates on top of basic circuit‑switched call control (ISO/IEC 11572) and uses generic supplementary‑service procedures (ISO/IEC 11582).
  • Protocol interactions and additional signalling requirements for interactions with other supplementary services and ANFs are specified.
• Operations and coding
  • Defines two ASN.1 operations: display and keypad (operation arguments and errors defined).
  • Uses ASN.1 and BER/CER/DER encoding (ITU‑T X.690); APDUs are carried in the Facility information element per ISO/IEC 11582.
  • Supports BMP strings for display/keypad content (normal and extended forms) and allows manufacturer extensions.
• Procedures and states
  • Client, Server and Transit PINX operational requirements and state machines are specified (SD‑Idle, etc.).
  • Includes message sequence examples (Annex B) and SDL representations (Annex C) for implementers.
• Interworking
  • Details behavior at gateway PINXs for interworking with public ISDN and non‑ISDN networks and interactions with services such as CLIP, CFU, MWI and mobility ANFs.

Applications and who uses it

• Vendors of PBX/PINX and enterprise telephony equipment implementing QSIG/SS‑SD.
• Telecom software developers building display/keypad dialog services between applications and users over PISNs.
• System integrators, testing laboratories and network architects who need protocol‑level interoperability across multi‑vendor private networks.
• Organizations deploying enterprise unified communications needing transparent keypad/display exchanges (e.g., remote interactive services, legacy terminal emulation).

Related standards

• ISO/IEC 21407 (service specification, stage 1/2)
• ISO/IEC 11572 (circuit switched call control)
• ISO/IEC 11582 (generic supplementary‑service procedures)
• ISO/IEC 11579‑1 (Q reference point definition)
• ITU‑T X.690, X.208/X.209 (ASN.1 encoding and notation)

Keywords: ISO/IEC 21408, SS‑SD, Simple Dialog supplementary service, QSIG, PISN, PINX, signalling protocol, ASN.1, Facility information element.