Overview
ISO/IEC TR 9575:1995 - "Information technology - Telecommunications and information exchange between systems - OSI Routeing Framework" is a Technical Report (second edition) that defines a conceptual framework for developing OSI-layer routing protocols. It describes the routeing (routing) functions required within the OSI Network Layer, clarifies the difference between routeing and relaying, and aims to expedite the standardization and interoperability of OSI routing protocols. The report reflects the state of OSI routing as of 1995 and adds options for using multicast subnetworks to interconnect routing and administrative domains.
Key topics and technical requirements
- Functional decomposition of routing: the report breaks routing into four interrelated aspects to simplify protocol design:
- Routing Information Base (RIB) - the complete set of routing data used by an End System (ES) or Intermediate System (IS).
- Information collection - how ES/IS obtain routing data (measurements, directory lookups, management input, routing protocols).
- Information distribution - how routing data is shared (routing protocols, management interfaces).
- Route calculation and maintenance - internal functions that generate the Forwarding Information Base (FIB) and maintain routes (including ageing and updates).
- F1 and F2 functions: two essential per-packet decision functions - F1 derives the next network relay or destination, F2 chooses the actual network entity to forward to, using inputs such as called/calling NSAPs, source routes and QoS.
- OSI-specific concepts and definitions: Administrative Domain, Routing Domain, Common Domain, NSAP, NPDU, SNPA, SNARE, BIS, ES, IS, hops, black holes, multicast subnetworks and multicast communication.
- Support for multicast subnetworks: second edition adds options for interconnecting routing/administrative domains and providing intra-domain connectivity using multicast-capable subnetworks.
- Interplay with management: routing information exchange and policy integration with OSI management functions.
Practical applications
- Provides a structured framework for designing and specifying OSI routing protocols and routing exchanges between systems.
- Guides implementers building OSI Network Layer stacks for interoperability across heterogeneous subnetworks and administrative boundaries.
- Helps network architects and system integrators design routing policies that consider QoS, source routing, and multi-domain routing.
- Useful for standardization bodies and protocol designers to harmonize routing protocol development and review prior to producing international standards.
Who should use this standard
- Network protocol designers and implementers working on OSI-based routing.
- Vendors developing OSI network-layer products or gateways between diverse subnetworks.
- Standards developers, systems integrators, and researchers focused on multi-domain routing, multicast transport, and OSI interoperability.
Related standards
- ISO/IEC 8648 - OSI Internal Organization of the Network Layer
- ISO/IEC 9542 - ES‑IS routing exchange protocol
- ISO/IEC 10589 - IS‑IS intra-domain routing protocol
- ISO/IEC 8473 - Connectionless-mode Network Service (CLNS) protocol
- ISO/IEC 8348 / ITU‑T X.213 - Network addressing definitions
Keywords: ISO/IEC TR 9575, OSI Routeing Framework, OSI routing, routing information base, forwarding information base, multicast subnetwork, administrative domain, routing domain, network layer routing.