The UDS protocol has become a de facto standard in automotive diagnostic applications. It is standardized as ISO 14229. UDS describes the implementation of various diagnostic services you can access through the protocol.

As UDS uses messages of variable byte lengths, a transport protocol is necessary on layers with only a well defined (short) message length, such as CAN or LIN. The transport protocol splits a long UDS message into pieces that can be transferred over the network and reassembles those pieces to recover the original message.

UDS runs on CAN, LIN, and Ethernet on various transport protocols.
Note   The Automotive Diagnostic Command Set supports only the ISO TP (standardized in ISO 15765-2), manufacturer-specific VW TP 2.0 transport protocols, and Diagnostic Over IP (ISO 13400).