This part of ISO 14229 specifies data link independent requirements of session layer services.

This part of ISO 14229 specifies common session layer services to provide independence between unified diagnostic services (ISO 14229‑1) and all transport protocols and network layer services (e.g. ISO 15765‑2 DoCAN, ISO 10681‑2 Communication on FlexRay, ISO 13400 DoIP, ISO 14230‑2 DoK-Line, etc.)

This part of ISO 14229 specifies a common service primitive interface between OSI layer 4 (Transport) and layer 5 (Session) via so-called service request/confirmation/indication primitives. This interface allows seamless implementation of ISO 14229‑1 Unified diagnostic services (UDS) with any communication protocol titled "DoXYZ / CoXYZ" like ISO 15765 DoCAN – Diagnostic communication over Controller Area Network, ISO 13400 DoIP, ISO 10681 Communication over FlexRay, ISO 14230 DoK-Line.

ISO 15031 (emissions-related OBD) and ISO 27145 (WWH-OBD) support the standardized service primitive interface.