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CAN/CSA-ISO/IEC 11584-97: Inter-exchange Signalling Protocol for Call Completion Supplementary Services in Private Integrated Services Networks
Scope, Technical Requirements, and Compliance Considerations for PISN Call Completion Signalling
Scope and Introduction
CAN/CSA-ISO/IEC 11584-97 is the Canadian adoption of the international standard ISO/IEC 11584:1997, titled Information technology – Telecommunications and information exchange between systems – Private Integrated Services Network – Inter-exchange signalling protocol – Call completion supplementary services. This standard specifies the signalling protocol at the Q reference point for call completion supplementary services within a Private Integrated Services Network (PISN).
The primary services addressed are:
- Completion of Calls to Busy Subscriber (CCBS) – allows a calling user to be notified and the call automatically resumed when the destination busy condition clears.
- Completion of Calls on No Reply (CCNR) – provides automatic call completion when the called party does not answer within a specified period.
The standard defines the Layer 3 protocol procedures, messages, and state transitions for inter-exchange signalling over the Q reference point. It forms part of the larger ISO/IEC PISN protocol suite and ensures interoperability between PISN exchanges from different manufacturers.
Service Component Symbol Description Call Completion to Busy Subscriber CCBS Permits recall when the destination line becomes idle Call Completion on No Reply CCNR Automatic call completion after ring-no-answer timeout Call Completion Timeout CCT Controls maximum duration of call completion monitoring
Note: CAN/CSA-ISO/IEC 11584-97 is an identical adoption of ISO/IEC 11584:1997, meaning no technical modifications have been made for the Canadian context. The standard number is often written as CAN/CSA-ISO/IEC 11584-97 (R2021) if reaffirmed.
Technical Requirements for the Signalling Protocol
The standard defines the inter-exchange signalling protocol using a state-machine approach. Exchanges (PINXs) communicate via a set of messages and information elements at the Q reference point, as defined in the companion standard ISO/IEC 11574 for basic circuit-mode services.
Protocol Structure and Messages
The protocol operates at Layer 3 of the OSI model. The following categories of messages are specified for call completion:
- Request/Response messages (e.g., SETUP, ALERTING, CONNECT)
- Notification messages to indicate service activation or deactivation
- Facility messages for supplementary service control
Message Code Function FACILITY 0x28 Carries call completion request/response information REGISTER 0x26 Used for remote service activation/deactivation INFORMATION 0x2F Convey supplementary control information during call NOTIFY 0x2E Indicates call completion status to the user (e.g., recall)
Information Elements and Procedures
Key information elements include:
- Call Completion Indicator (CSI) – identifies the requested service (CCBS/CCNR).
- Call Completion Correlator – links the original call to the completion attempt.
- Call Completion Status – reports progress (e.g., pending, confirmed, failed).
Procedures cover:
- Activation/Deactivation: User-initiated service activation via keypad or feature activation sequences that generate appropriate FACILITY messages.
- Invocation and Execution: When a call fails with busy or no-reply, the originating exchange stores the call parameters and monitors the destination line. Upon receiving a line free indication, it attempts re‑establishment automatically.
- Timer Management: Timers T-CCBS and T-CCNR govern the duration of monitoring; if expired, the service is cancelled.
Implementation Tip: To ensure seamless interaction with other supplementary services (e.g., call forwarding, call transfer), the protocol stack must implement the state machines exactly as specified in Annex A of ISO/IEC 11584. Many interoperability issues arise from non‑compliant timer values.
Implementation and Compliance
Adoption of CAN/CSA-ISO/IEC 11584-97 is voluntary in Canada, but it is widely referenced by Canadian carriers and manufacturers to guarantee interconnectivity in private networks. Compliance requires:
- Conformance to the Layer 3 protocol specification: Messages, states, and coding must match the standard exactly.
- Interoperability testing with a reference implementation or using a conformance test suite based on ISO/IEC 11584′s Protocol Implementation Conformance Statement (PICS) proforma.
- Documentation: A PICS document must declare which capabilities (CCBS, CCNR, or both) are implemented, plus any optional features such as the “Call Completion on Busy/No Reply” combination.
Warning: Earlier versions of the standard (e.g., ISO/IEC 11584:1994) used different message codings. Equipment certified against the 1994 version is not automatically compatible with CAN/CSA-ISO/IEC 11584-97. Updates to timers and state machines may affect interoperability.
Certification in Canada
The CSA (Canadian Standards Association) has published this standard in its national catalogue. For regulatory requirements, especially when interconnecting with public networks, implementation should also consider the applicable sections of the Canadian Telecommunications Standards (e.g., CS-03). However, for purely private PISN networks, compliance with CAN/CSA-ISO/IEC 11584-97 is sufficient to demonstrate technical conformity.
Benefits of Compliance: Fully compliant PISN equipment provides users with reliable call completion services across multi‑vendor exchanges, reducing user abandonment and improving network efficiency. CCBS can reduce the number of repeated manual redial attempts by up to 50% in high‑volume environments.
Frequently Asked Questions
Q: Is CAN/CSA-ISO/IEC 11584-97 still current in Canada?
A: The standard has been reaffirmed multiple times. As of 2025, the current version is CAN/CSA-ISO/IEC 11584-97 (R2021). Users should check the CSA website for the latest reaffirmation status.
A: The standard has been reaffirmed multiple times. As of 2025, the current version is CAN/CSA-ISO/IEC 11584-97 (R2021). Users should check the CSA website for the latest reaffirmation status.
Q: What is the relationship between ISO/IEC 11584 and other PISN standards?
A: It is part of the ISO/IEC 1157x and 1158x series. It works in conjunction with ISO/IEC 11574 (basic circuit-mode services) and ISO/IEC 11582 (generic functional procedures). The protocol defined in 11584 complements the service description found in ISO/IEC 11584-1.
A: It is part of the ISO/IEC 1157x and 1158x series. It works in conjunction with ISO/IEC 11574 (basic circuit-mode services) and ISO/IEC 11582 (generic functional procedures). The protocol defined in 11584 complements the service description found in ISO/IEC 11584-1.
Q: Can equipment certified to the original ISO/IEC 11584:1997 be used without modification in Canadian networks?
A: Yes, because CAN/CSA-ISO/IEC 11584-97 is an identical adoption. However, equipment must also comply with Canadian safety and electromagnetic compatibility (EMC) regulations (e.g., ICES-003). The protocol level will be fully compatible.
A: Yes, because CAN/CSA-ISO/IEC 11584-97 is an identical adoption. However, equipment must also comply with Canadian safety and electromagnetic compatibility (EMC) regulations (e.g., ICES-003). The protocol level will be fully compatible.
Q: Does this standard support SIP-based networks?
A: No. CAN/CSA-ISO/IEC 11584-97 is designed for the traditional ISDN‑based Q‑reference point protocol (Q‑SIG). Migrations to SIP‑based PISN may use equivalent services defined in other standards, such as IETF RFC 5552 for CCBS/CCNR.
A: No. CAN/CSA-ISO/IEC 11584-97 is designed for the traditional ISDN‑based Q‑reference point protocol (Q‑SIG). Migrations to SIP‑based PISN may use equivalent services defined in other standards, such as IETF RFC 5552 for CCBS/CCNR.