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Scope and Purpose
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Scope and Purpose
ISO/IEC 10035-2 (adopted as CAN CSA ISO IEC 10035-2-01) defines the Protocol Implementation Conformance Statement (PICS) proforma for the connectionless mode of the Association Control Service Element (ACSE) in Open Systems Interconnection (OSI). This standard complements ISO/IEC 10035-1, which specifies the connectionless ACSE protocol itself. The PICS proforma is a structured questionnaire that allows implementers to declare which capabilities, options, and parameters of the protocol are supported, thereby facilitating interoperability testing and conformance assessment.
The scope of this part covers the PICS for the ACSE connectionless service element used in application layer communications. It applies to implementations claiming conformance to the connectionless ACSE protocol defined in ISO/IEC 10035-1. The proforma is intended for use by test laboratories, developers, and users to verify that an implementation conforms to the protocol specification. It systematically addresses mandatory and optional features, timers, protocol parameters, and supported abstract syntaxes.
As a Canadian adoption, CAN CSA ISO IEC 10035-2-01 incorporates the original ISO/IEC text without deviation, ensuring alignment with international conformance testing practices. The document is part of the OSI conformance testing framework (ISO/IEC 9646 series) and is critical for achieving formal certification of ACSE implementations in sectors such as telecommunications, industrial automation, and government networks.
Technical Requirements of the PICS Proforma
The PICS proforma defined in ISO/IEC 10035-2 is organized into tables that cover major protocol functions. Each table lists features with a status column (mandatory M, optional O, conditional C) and a support column to be filled by the implementer. The following table summarizes the key areas addressed by the proforma:
| Table | Feature / Group | Mandatory Items | Optional Items |
|---|---|---|---|
| Table 1 | Protocol version identification | Version 1 | – |
| Table 2 | ACSE protocol procedures (connectionless) | A-ASSOCIATE, A-RELEASE, A-ABORT, P-ABORT | – |
| Table 3 | APDU handling (A-ASSOCIATION, A-RELEASE, A-ABORT, P-ABORT) | Syntax, encoding rules (ASN.1/BER) | Additional external wrapper APDUs |
| Table 4 | Timer and retry parameters | – | T–inactivity, T–response, retry counts |
| Table 5 | Supported application context names | At least one context | Multiple contexts |
| Table 6 | Constraints on APDU sizes (max length) | Minimum: 512 octets | Larger limits (e.g., 2^16-1) |
For each table, the implementer must provide the implementation details, including any limitations or deviations. Conditional items (C) require the support of specific other features; their status is determined by the implementer’s answers in preceding tables. The proforma also includes a set of standardized statements about the implementation’s initialization and termination behavior.
Implementation Highlights
Successful implementation according to ISO/IEC 10035-2 requires careful mapping of the ACSE connectionless protocol onto the underlying presentation service (ISO/IEC 8823). The PICS proforma helps developers identify which protocol elements must be supported for conformance. Key implementation considerations include:
- Abstract syntax negotiation: The implementation must support at least one application context that defines the abstract syntax and transfer syntax for ACSE APDUs. The PICS proforma requires clear declaration of supported context names and their associated encoding rules (e.g., ASN.1 distinguished encoding).
- Timer configuration: While timers like T–inactivity and T–response are optional in the standard, many real-world deployments require them for robust operation. The proforma makes their support explicit, enabling testers to verify timeout behavior during conformance tests.
- Encoding constraints: The maximum APDU size must be stated, along with any limitations on nesting of wrappers (e.g., for A-ASSOCIATION APDUs). The proforma includes provisions for extended length fields, which are critical in high-delay networks.
- Error handling: Mandatory APDU types (A-ABORT, P-ABORT) must be correctly generated and received. The PICS proforma allows implementers to list supported abort information fields and external diagnostic codes.
Tip: When filling out the PICS proforma, always start with the mandatory items and record the exact version of the abstract syntax used. Many conformance failures stem from mismatched application context names or missing mandatory APDU support.
Compliance and Conformance Notes
Conformance to ISO/IEC 10035-2 is evaluated by a test laboratory using the static conformance review (statements in the PICS) and dynamic tests (protocol behavior). The following points are critical for achieving compliance:
- Complete declaration: Every mandatory item in the proforma (marked “M”) must be supported. Omission or a “not implemented” response for a mandatory item results in non-conformance.
- Consistency across the stack: The ACSE PICS must align with the PICS of the underlying presentation and session layers (ISO/IEC 8823-2, ISO/IEC 8327-2). Test campaigns often check cross-layer dependencies.
- Conditional support: Items with status “C” must be re-evaluated based on responses to other tables. A common oversight is forgetting to support conditional features when preconditions are met (e.g., supporting APDU size extension if the implementation claims to support large APDUs).
- Testing of optional features: Optional features (status “O”) do not need to be implemented, but if claimed, they must be tested. The PICS proforma must accurately reflect the implementation’s state.
Important: Some national adoptions (including the Canadian adoption CAN CSA ISO IEC 10035-2-01) may include a National Annex with additional requirements for specific fields such as emergency communications. Always check the local adoption when seeking certification in a particular jurisdiction.
Success path: A properly completed PICS proforma that matches the implementation’s true capabilities greatly reduces test execution time. Many test labs use automated tools to parse the PICS and select relevant test cases.
Non-conformance risk: Failing to declare a mandatory APDU (e.g., A-ABORT) or providing contradictory answers about supported timers can cause the entire conformance assessment to be rejected. The PICS is legally binding in procurement contracts for OSI-compliant systems.
FAQs
Q: What is the difference between ISO/IEC 10035-1 and ISO/IEC 10035-2?
A: Part 1 specifies the protocol itself (the syntax and procedures of the connectionless ACSE APDUs). Part 2 defines the PICS proforma, which is a standardized form that implementers must fill out to declare which parts of the protocol are implemented. The proforma is essential for conformance testing, while Part 1 provides the normative protocol definition.
A: Part 1 specifies the protocol itself (the syntax and procedures of the connectionless ACSE APDUs). Part 2 defines the PICS proforma, which is a standardized form that implementers must fill out to declare which parts of the protocol are implemented. The proforma is essential for conformance testing, while Part 1 provides the normative protocol definition.
Q: Is the PICS proforma mandatory for all ACSE implementations?
A: Yes, if an implementation claims conformance to the ACSE connectionless protocol, it must be accompanied by a completed PICS proforma that follows ISO/IEC 10035-2. This is specified in the conformance section of the protocol standard and is a prerequisite for formal OSI conformance testing.
A: Yes, if an implementation claims conformance to the ACSE connectionless protocol, it must be accompanied by a completed PICS proforma that follows ISO/IEC 10035-2. This is specified in the conformance section of the protocol standard and is a prerequisite for formal OSI conformance testing.
Q: Can the PICS proforma be used for both connection-oriented and connectionless ACSE?
A: No. ISO/IEC 10035-2 specifically covers the connectionless mode. The connection-oriented ACSE PICS is defined in a different standard—ISO/IEC 15953 (which superseded earlier parts of 10035). Implementers must use the correct proforma for the mode they are implementing.
A: No. ISO/IEC 10035-2 specifically covers the connectionless mode. The connection-oriented ACSE PICS is defined in a different standard—ISO/IEC 15953 (which superseded earlier parts of 10035). Implementers must use the correct proforma for the mode they are implementing.
This standard remains relevant for legacy OSI systems and some modern industrial protocols that rely on ACSE for application association management. Understanding the PICS proforma is key to maintaining interoperability in such environments.
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