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Understanding CAN/CSA-ISO/IEC 13863-02: Signalling Protocol for Call Completion in Private Integrated Services Networks
Technical requirements, implementation highlights, and compliance notes for the QSIG protocol supporting CCBS and CCNR services.
1. Scope and Applicability of CAN/CSA-ISO/IEC 13863-02
CAN/CSA-ISO/IEC 13863-02 is the Canadian national adoption of the international standard ISO/IEC 13863-2. This standard is a critical component of the Private Integrated Services Network (PISN) standards suite, specifically focusing on the inter-exchange signalling protocol (QSIG) at the Q reference point.
The standard specifies the signalling protocol for the support of the Call Completion supplementary services. The Q reference point defines the signalling boundary between two Private Integrated Services Network Exchanges (PINXs). The services explicitly covered are:
- Call Completion to Busy Subscriber (CCBS): Allows a user whose call fails because the destination is busy to request the network to monitor the destination. When the destination becomes free, the network recalls the requesting user and re-attempts the call establishment.
- Call Completion on No Reply (CCNR): Allows a user whose call fails because the destination does not answer to request the network to monitor the destination. When the destination becomes available (e.g., user returns or terminal activity is detected), the network recalls the requesting user.
This standard is intrinsically linked to the service description standard (typically ISO/IEC 13864), which defines the operational model and functional capabilities. The protocol defined here provides the precise formatting, sequencing rules, and error handling mechanisms for the exchange of signalling messages.
Scope Note: While this standard defines the protocol at the Q reference point, network engineers must consult the companion service description standards for a complete understanding of the user-to-network interface behaviour and overall feature interactions.
2. Technical Protocol Requirements
The core of CAN/CSA-ISO/IEC 13863-02 lies in its precise definition of the Signalling Protocol Data Units (SPDUs) communicated between PINXs. The protocol follows a client-server model where the requesting PINX (calling side) initiates a request to the remote PINX (called side) to manage the call completion lifecycle.
Key Protocol Elements:
- Call Completion Request: The calling PINX sends an invocation to activate the monitoring service on the called PINX for the specific user.
- Call Completion Execution: When the network-determined condition is met, the called PINX initiates a callback towards the calling PINX, requiring suspension and later re-establishment of the original call.
- Call Completion Cancellation: The user or the PINX can clear a pending request at any time through explicit signalling procedures.
Table 1: Core SPDU Operations for Call Completion Services
| SPDU Operation | Mnemonic | Description | Direction |
|---|---|---|---|
| ccRequest | CR | Request the monitoring of a specific user (Busy/No Reply) | Calling PINX → Called PINX |
| ccExecPossible | CP | The called PINX indicates the monitored condition has occurred (e.g., line free) | Called PINX → Calling PINX |
| ccExecNotify | CN | Confirms that the call completion execution is in progress on the calling side | Calling PINX → Called PINX |
| ccCancel | CL | Terminates a previously established Call Completion request | Either direction |
The protocol utilizes state tables and specific timers (e.g., T1 for initial request response, T2 for recall timing) to ensure robustness against network errors or lost messages. If a timer expires without the expected response, the transaction is considered failed, and appropriate resource clear-down procedures are executed.
Implementation Caution: The standard mandates strict adherence to the state transition tables defined in its normative annexes. Deviations in timer values or state sequencing can lead to protocol mismatches, “ghost” call completion requests, or resource exhaustion in the PINX.
3. Implementation and Interoperability Highlights
Implementing CAN/CSA-ISO/IEC 13863-02 involves integrating the precise protocol behaviour into a PINX or a gateway that interfaces with QSIG trunking networks. Key challenges and highlights include:
- State Machine Management: The protocol defines complex interlinked call states. The implementation must accurately manage the suspension of the original call leg and the establishment of the new Call Completion call leg (suspension, recall, and re-establishment phases).
- Resource Handling: The standard requires the network to suspend the original call and hold it until the recall condition is met. This demands careful memory management for held call references and associated notification information.
- Multi-Vendor Interoperability: Since QSIG is specifically designed for multi-vendor PISN environments, rigorous interoperability testing is critical. Subtle differences in proprietary QSIG stacks, despite formal adherence, can lead to service failures on the first recall attempt.
Interoperability Success: A robust implementation of CAN/CSA-ISO/IEC 13863-02 ensures that users connected to a PISN can flawlessly use CCBS and CCNR features across different vendor platforms (e.g., a vendor A PINX interacting with a vendor B or vendor C PBX over a T1/E1 QSIG link).
4. Compliance and Certification Requirements
In Canada, the CAN/CSA-ISO/IEC 13863-02 standard is the recognized authority for this specific protocol layer. Compliance involves a structured approach to conformance testing:
- Equivalency: The Canadian standard is technically identical to the international ISO/IEC 13863-02. Products certified against the ISO standard inherently meet the Canadian requirement.
- Protocol Implementation Conformance Statement (PICS): The standard includes a comprehensive PICS proforma. Any entity claiming compliance must complete this document, declaring which optional capabilities are implemented and which conditions are supported.
- Static and Dynamic Conformance: The standard outlines static conformance (which protocol elements must be implemented) and dynamic conformance (the correct protocol behaviour in every possible state).
The compliance framework ensures that a PINX product can be rigorously validated against the protocol requirements before deployment in a carrier or enterprise network.
Compliance Mandate: For telecommunications equipment being procured for Canadian federal infrastructure that interconnects several PISN sites, compliance with CAN/CSA-ISO/IEC 13863-02 is a mandatory pre-requisite. Suppliers must provide a completed PICS document demonstrating their protocol implementation conforms strictly to the standard to be eligible for procurement.
Frequently Asked Questions (FAQs)
Q: What is the precise difference between CAN/CSA-ISO/IEC 13863-02 and the base ISO/IEC 13863-02?
A: The Canadian version is an identical adoption of the international standard. It carries the CSA Group’s administrative foreword and may include minor editorial comments, but the technical specification, protocol definitions, and testing mandates are 100% equivalent to the ISO/IEC 13863-02 standard.
A: The Canadian version is an identical adoption of the international standard. It carries the CSA Group’s administrative foreword and may include minor editorial comments, but the technical specification, protocol definitions, and testing mandates are 100% equivalent to the ISO/IEC 13863-02 standard.
Q: Which specific supplementary services are covered under this protocol?
A: This standard specifically defines the signalling protocol for two Call Completion supplementary services: Call Completion to Busy Subscriber (CCBS) and Call Completion on No Reply (CCNR). It does not cover other services like Call Forwarding or Call Transfer, which are defined in other parts of the broader ISO/IEC 13863 series and respective service standards.
A: This standard specifically defines the signalling protocol for two Call Completion supplementary services: Call Completion to Busy Subscriber (CCBS) and Call Completion on No Reply (CCNR). It does not cover other services like Call Forwarding or Call Transfer, which are defined in other parts of the broader ISO/IEC 13863 series and respective service standards.
Q: Is CAN/CSA-ISO/IEC 13863-02 relevant to modern IP-based communication systems?
A: Yes. While originally designed for circuit-switched ISDN networks (QSIG), the standardized protocol logic for call completion has directly influenced the same features in modern IP-PBXs and SIP-based networks (e.g., SIP CCBS/CCNR defined in RFC 6910). Understanding the QSIG model is essential for legacy system integration and ensuring feature transparency across hybrid TDM/IP enterprise networks.
A: Yes. While originally designed for circuit-switched ISDN networks (QSIG), the standardized protocol logic for call completion has directly influenced the same features in modern IP-PBXs and SIP-based networks (e.g., SIP CCBS/CCNR defined in RFC 6910). Understanding the QSIG model is essential for legacy system integration and ensuring feature transparency across hybrid TDM/IP enterprise networks.
Q: What is the role of a PINX in the context of this standard?
A: A Private Integrated services Network Exchange (PINX) is the physical or virtual node that implements the protocol. It can be a traditional PBX, a key system, an IP-PBX, or a converged switch. The PINX uses the Q reference point to communicate with other PINXs. This standard defines exactly how two PINXs exchange signalling messages over the Q reference point to provide call completion services to their respective attached users.
A: A Private Integrated services Network Exchange (PINX) is the physical or virtual node that implements the protocol. It can be a traditional PBX, a key system, an IP-PBX, or a converged switch. The PINX uses the Q reference point to communicate with other PINXs. This standard defines exactly how two PINXs exchange signalling messages over the Q reference point to provide call completion services to their respective attached users.
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