DoIP

DoIP stands for Diagnostics over Internet Protocol; the ISO 13400 series formally calls it Diagnostic communication over Internet Protocol. It defines how diagnostic testers discover vehicles on a network, activate routing through the vehicle gateway and exchange UDS (ISO 14229) messages over TCP and UDP on port 13400, with optional TLS added in the 2019 edition of ISO 13400-2.

Both carry the same UDS diagnostic services; the difference is the transport. Diagnostics over CAN (DoCAN, ISO 15765) splits messages into small CAN frames and is limited by CAN bit rates, while DoIP uses Ethernet and TCP/IP for far higher throughput. That makes DoIP the preferred path for flashing large software images, while DoCAN remains common on CAN-only ECUs.

DoIP is used at the vehicle's diagnostic access point: a tester or flashing station connects to the Ethernet pins of the OBD connector and talks to the DoIP gateway. It is also used on production lines for end-of-line programming. Because it exposes powerful services, DoIP access is typically protected with UDS authentication and gateway firewalling.