Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Understanding CAN/CSA-ISO/IEC 13865-04: Private Integrated Services Network (PISN) Call Transfer Supplementary Service
Technical Requirements, Implementation, and Compliance for the Inter-exchange Signalling Protocol
Scope and Overview
CAN/CSA-ISO/IEC 13865-04 is the Canadian adoption of the international standard ISO/IEC 13865:2004, which defines the inter-exchange signalling protocol for the Call Transfer supplementary service within a Private Integrated Services Network (PISN). This standard is part of the broader series of standards for PISN signalling and is essential for ensuring interoperability among different vendors’ equipment in private telecommunication networks.
Applicability
The standard applies to private telecommunications networks that utilise the Private Integrated Signalling Protocol (PISN) based on ISDN techniques. It specifies the protocol procedures, message formats, and state transitions necessary for a user (the transferor) to transfer an active call to another user (the recipient). The standard covers both basic call transfer and scenarios involving multiple connections, such as consultation and completion of transfer.
Tip: While this standard is widely adopted in North America via CAN/CSA, it is identical in technical content to the original ISO/IEC 13865:2004, making it suitable for global PISN implementations.
Technical Requirements
Signalling Protocol Architecture
The protocol operates at the network layer of the PISN stack, relying on the inter-exchange signalling messages defined in the ISO/IEC 13864 series. The Call Transfer supplementary service uses specific messages to initiate, progress, and complete the transfer operation. Key message types include:
| Message | Code | Function |
|---|---|---|
| INFORMATION | 0x0E | Carries call transfer invocation parameters |
| FACILITY | 0x49 | Transfers supplementary service requests/responses |
| CALL PROCEEDING | 0x02 | Acknowledges transfer request processing |
| ALERTING | 0x01 | Indicates that the recipient is being alerted |
| CONNECT | 0x07 | Completes the call transfer |
State Machine and Procedures
The transferor follows specific state transitions to ensure reliable transfer. Upon invocation, the transferor sends a FACILITY message with the transfer identifier to the destination exchange. The protocol discriminator must be set to the PISN supplementary service value (0x02). The standard defines mandatory information elements such as call identity, transfer number, and invocation context.
Implementation Success: When developing a private exchange (PBX) that supports call transfer, ensure the state machine conforms to the tables in Annex A of the standard. Proper handling of the “Transfer Request – Pending” state is critical to avoid dropped calls.
Compatibility and Interworking
The standard ensures backward compatibility with earlier versions of the PISN protocol series. It also defines interworking with the public ISDN supplementary service for call transfer (ETSI TS 183 003). The use of a common application entity (CAE) reference model facilitates interworking across different network types.
Caution: When integrating CAN/CSA-ISO/IEC 13865-04 equipment with non-compliant terminals, the network may fall back to basic call transfer only, losing features like consultation hold and explicit notification.
Implementation Highlights
Parameter Coding
All signalling parameters are coded according to the Tag-Length-Value (TLV) scheme. For example, the transfer number parameter uses tag 0x06, length up to 10 octets, and value containing the called party number in E.164 format. The standard mandates that the transferor includes its own identification to prevent fraudulent transfer requests.
Testing and Verification
Conformance testing is specified in ISO/IEC 13865-2 (not part of this standard), but implementers should follow the abstract test suite described in that companion document. A typical test sequence involves three PISN exchanges: transferor exchange, current call exchange, and recipient exchange.
Tip: Use a protocol analyser capable of decoding PISN messages with supplementary service elements. Validate that the “Transfer Complete” message includes the correct connection identifiers to ensure loop-free connections.
Compliance and Certification Notes
In Canada, compliance with CAN/CSA-ISO/IEC 13865-04 is typically required for equipment sold to government or enterprise clients that demand adherence to CSA standards. Certification involves submitting a self-declaration or obtaining a third-party test report from an accredited laboratory.
Documentation and Markings
Products claiming compliance should include a reference to CAN/CSA-ISO/IEC 13865-04 in their user manual or technical datasheet. The CSA certification mark may be used if the product has been certified by CSA Group.
Important: Non-compliance with this standard in a PISN deployment can lead to interoperability failures, such as call transfers being rejected or calls being dropped due to incorrect state handling. Always verify that all network elements are updated to the same version of the standard.
This standard is maintained by the joint technical committee ISO/IEC JTC 1/SC 6. The Canadian adoption is overseen by the CSA Group’s technical committee on telecommunications. Revisions are expected to align with future developments in the ISO/IEC 13865 series.
Q: What is the primary purpose of CAN/CSA-ISO/IEC 13865-04?
A: It specifies the signalling protocol for the Call Transfer supplementary service in a Private Integrated Services Network, enabling users to transfer an active call to another terminal without operator intervention.
A: It specifies the signalling protocol for the Call Transfer supplementary service in a Private Integrated Services Network, enabling users to transfer an active call to another terminal without operator intervention.
Q: Does this standard apply to wireless PISN systems?
A: Yes, the protocol is independent of the underlying access technology and can be used in both wired and wireless private networks, as long as they use ISDN-based signalling.
A: Yes, the protocol is independent of the underlying access technology and can be used in both wired and wireless private networks, as long as they use ISDN-based signalling.
Q: How is this standard different from public network call transfer protocols?
A: It is designed for private network interoperability and uses a dedicated message set and state machine that may differ from the public ISDN or SIP-based call transfer defined in other standards. Interworking functions are defined to bridge the two domains.
A: It is designed for private network interoperability and uses a dedicated message set and state machine that may differ from the public ISDN or SIP-based call transfer defined in other standards. Interworking functions are defined to bridge the two domains.
Q: Is certification mandatory in Canada?
A: Certification is not mandatory by law, but many procurement contracts for PBX and network equipment require compliance with CAN/CSA standards, including this one, to ensure interoperability in multi-vendor environments.
A: Certification is not mandatory by law, but many procurement contracts for PBX and network equipment require compliance with CAN/CSA standards, including this one, to ensure interoperability in multi-vendor environments.