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IEC 62443-3-3 Clause 11 – Resource Availability

ISA/IEC 62443-3-3, Clause 11 defines Foundational Requirement FR 7 (RA) and the associated system requirements (SRs) and requirement enhancements (REs) used when claiming Security Level capability for this FR.

Keep essential control-system resources available and resilient against denial-of-service and resource exhaustion.

Teaching note: Summaries paraphrase ISA/IEC 62443-3-3 for learning. They are not verbatim extracts — always use the published standard for normative wording, RE text and SL mappings (see Annex B).

Reference: ISA/IEC 62443-3-3, Clause 11
Related: Foundational Requirements overview | FR / SL Vector | Annex B mapping | Security Levels

FR pages: FR 1 | FR 2 | FR 3 | FR 4 | FR 5 | FR 6 | FR 7

Purpose

Keep essential control-system resources available and resilient against denial-of-service and resource exhaustion.

Requirement enhancements under each SR raise the capability needed for higher SL-C(RA) claims. Exact RE text and which SL columns they populate are in the standard and Annex B.

System requirements in this FR

SR summaries

SR 7.1: Denial of service protection

Reference: ISA/IEC 62443-3-3, Clause 11 (SR 7.1)

Summary
The control system shall protect against denial-of-service conditions affecting essential functions, within stated assumptions.

SR 7.2: Resource management

Reference: ISA/IEC 62443-3-3, Clause 11 (SR 7.2)

Summary
Resources (CPU, memory, bandwidth, handles) shall be managed so critical services are not starved by non-critical demand.

SR 7.3: Control system backup

Reference: ISA/IEC 62443-3-3, Clause 11 (SR 7.3)

Summary
Backup capability shall exist for control-system information needed for recovery.

SR 7.4: Control system recovery and reconstitution

Reference: ISA/IEC 62443-3-3, Clause 11 (SR 7.4)

Summary
After disruption, the control system shall be recoverable/reconstitutable to a known secure state.

SR 7.5: Emergency power

Reference: ISA/IEC 62443-3-3, Clause 11 (SR 7.5)

Summary
Emergency power considerations shall support security and essential functions during power events as required.

SR 7.6: Network and security configuration settings

Reference: ISA/IEC 62443-3-3, Clause 11 (SR 7.6)

Summary
Network and security configuration settings shall be defined, managed and hardened (less functionality / documented baselines).

SR 7.7: Least functionality

Reference: ISA/IEC 62443-3-3, Clause 11 (SR 7.7)

Summary
Only required functions, ports, protocols and services shall be enabled (least functionality).

SR 7.8: Control system component inventory

Reference: ISA/IEC 62443-3-3, Clause 11 (SR 7.8)

Summary
A component inventory for the control system shall be maintained to support availability and recovery decisions.

Key takeaways