ISO/IEC 9594-9:2020

Overview

ISO/IEC 9594-9:2020 - Information technology - Open systems interconnection - Part 9: The Directory: Replication defines the Directory shadow service used by Directory System Agents (DSAs) to replicate Directory information. The standard specifies how Directory information (the Directory Information Base or DIB) can be copied and updated between DSAs using the Directory Information Shadowing Protocol to improve availability, performance and service to Directory users. Annex A provides the ASN.1 module for the abstract shadow service.

Key topics and technical requirements

• Shadow service and shadowing: Defines the shadow service semantics and the process of shadowing (replication) between a shadow supplier and a shadow consumer.
• Shadowed information: Specifies the structure and scope of replicated data, including replicated area, replication base entry, shadowed DSA specific entry (SDSE), attribute completeness and subordinate completeness.
• Operational bindings: Details the shadow operational binding characteristics and the DSA procedures for creating, managing and terminating operational bindings between supplier and consumer.
• Shadowing agreement: Describes required terms for shadowing agreements, including the unit of replication, update mode (primary/secondary shadowing distinctions), and supplier/consumer references.
• Shadow operations and protocol: Defines the set of shadow operations (e.g., Coordinate Shadow Update, Request Shadow Update, Update Shadow, and DSA Shadow Bind/Unbind) and expected protocol behaviors for synchronization.
• Error handling and consistency: Includes shadow error types, last update and update window concepts to detect and handle replication problems.
• Distinction from caching: Clarifies that caching is outside the Directory specification, while shadowing is a managed replication service.
• ASN.1 module: Annex A supplies the ASN.1 definition needed for implementers to encode the abstract shadow service.

Applications and who uses this standard

ISO/IEC 9594-9:2020 is intended for:

• Directory implementers building X.500-compatible DSAs or enterprise directory solutions that require robust replication.
• System architects and network engineers designing distributed directory/topology for high availability, load distribution and geographic replication.
• Security and identity management teams integrating replicated directory data with authentication, authorization and PKI infrastructures.
• Standards bodies and integrators creating industry profiles that rely on a common Directory replication framework.

Practical uses include replicating directory entries across data centers, maintaining copies of naming contexts, and coordinating updates between master and secondary DSAs to ensure consistent Directory service.

Related standards

• ISO/IEC 9594 series (Parts 1–8) - Overview, models, services, protocols and attribute/object definitions (e.g., ISO/IEC 9594-1, -2, -3, -4, -5, -6, -7, -8)
• ISO/IEC 8824-1 (ASN.1) - Abstract Syntax Notation One used for the ASN.1 module in Annex A

Keywords: ISO/IEC 9594-9:2020, Directory replication, shadowing, Directory System Agent (DSA), Directory Information Shadowing Protocol, shadow operational binding, ASN.1.