Its Data Bus - Thin Transport Layer
This SAE Recommended Practice details the Thin Transport Layer of the Intelligent Transportation Systems (ITS) Data Bus, which is generally intended for in-vehicle use.
The Thin Transport Layer sits between SAE J2366-2 and J2366-7. It provides the handling of such activities as the packetizing of long messages and message reassembly. Design of the messages and headers has stressed economy, in terms of bits within a CAN 2.0B frame.
The ITS Data Bus (IDB) is a non-proprietary virtual token passing bus, designed to allow disparate consumer, vehicle, and commercial electronic components to communicate and share information across a standard, open data bus.