Overview
ISO/IEC 11575:1995 defines principled protocol mappings between the OSI Data Link Service (DLS) and common Data Link protocols. It covers both connection-mode (CO‑DLS) and connectionless‑mode (CL‑DLS) operation and specifies detailed mappings (M1, M2, M5, M6) and the main features of mappings M3 and M4. The standard is normative about how Network‑layer protocols that reference the OSI Data Link Service map onto real Data Link protocols (HDLC variants, X.25 LAPB-compatible SLP, LLC Types 1 and 2), but it does not prescribe specific product implementations.
Key topics
- Scope of mappings: Defines how CO‑DLS and CL‑DLS primitives and parameters relate to PDUs and procedures of standard Data Link protocols (HDLC, LAPB, LLC).
- Detailed mappings: Formal mappings M1, M2, M5 and M6 are specified; M3 and M4 are described at the feature level.
- DLS model and architecture: Concepts such as DLS user/provider, DLSAP, DL‑entity, DL‑PDU and DLSDU; support for point‑to‑point, centralized multipoint and distributed multipoint links.
- Service primitive modelling: Uses a rendezvous model for DLS user primitives (request/response) and an immediate‑occurrence model for provider primitives (indication/confirm), clarifying timing assumptions in mappings.
- Function mapping: How DLSDUs (DL‑DATA or DL‑UNITDATA) map to the protocol’s basic data transfer unit (typically the Information field of a single frame), and how connection setup, reset and release map to protocol procedures.
- Conformance role: Acts as the “glue” between Network‑layer standards (that specify use of DLS) and Data Link protocol standards (that define procedures and PDUs), enabling precise interoperability criteria.
Applications
ISO/IEC 11575:1995 is practical for:
- Network protocol designers who specify Network‑layer behavior in terms of the OSI Data Link Service and need exact mappings to HDLC, LAPB, or LLC implementations.
- Firmware and driver developers implementing Data Link protocols and ensuring correct behavior when supporting OSI‑style services.
- Test labs and conformance bodies validating that Network‑layer implementations correctly use underlying Data Link protocols.
- System integrators and network architects planning interoperability between legacy Data Link technologies and upper‑layer protocols.
Related standards
Key referenced standards include ISO/IEC 8886 (DLS definition), ISO/IEC 3309 / 4335 / 7809 (HDLC frame structure and procedures), ISO/IEC 7776 (LAPB‑compatible SLP), and ISO/IEC 8802‑2 (LLC). For consistent interoperability work, consult these alongside ISO/IEC 11575:1995.
Keywords: ISO/IEC 11575:1995, OSI Data Link Service, protocol mappings, HDLC, X.25 LAPB, LLC, connection‑mode, connectionless‑mode, DLSDU, DLSAP, conformance.
