DoIP – Diagnostics over IP

Historically, vehicle manufacturers developed diagnostic services over proprietary protocols. Over time and due to the requirements of complexity, diagnostics has shifted to the common Unified Diagnostic Services (UDS) protocol that supports various BUS systems such as CAN, K-line, FlexRay and Ethernet.

In a vehicle with Diagnostics over Internet Protocol (DoIP), it typically has one Gateway ECU to transfer all diagnostic messages between the external test system (via the J1962 / OBDII port) on ethernet and other ECUs on other vehicle networks.

DoIP is the packaging of diagnostic messages in Ethernet frames for communication of a diagnostic system with a vehicle.

DoIP uses Ethernet 100 Base-TX instead of CAN (typically 500kbps) and subsequently provides a much greater bandwidth

DoIP is the diagnostic transport protocol as defined in ISO 13400, and uses the standardised diagnostic protocol UDS as defined in ISO 14229-5, these services are identical to UDS used in CAN

DoIP transport layer is defined as a part of the UDS specification and the ISO model below shows the inter relationships

Application (Diagnostics):

Application LayerDoIP
Presentation LayerUDS Application Layer (ISO14229-5)
Session LayerDoIP Transport Layer (ISO13400-2)
Transport LayerTCP-IP / UDP
Network LayerIPV 4 / IPV 6
Data Link LayerEthernet MAC
Physical LayerBroad Reach or 100 Base T