The Diagnostics over Internet Protocol (DoIP) is a standardized communication protocol (ISO 13400) for performing vehicle diagnostics and software updates over Ethernet. It enables faster and more efficient communication between diagnostic tools and vehicle ECUs compared to legacy in-vehicle networks like CAN. Within DoIP, there are two key DoIP Protocol connection types, Option 1 and Option 2. These options define how a diagnostic tool establishes a connection with a vehicle network. Lets discuss these two DoIP Protocol connection types.
Table of Contents
DoIP Protocol connection types: Option 1 (Direct Physical)
DoIP Option 1 refers to a direct physical Ethernet connection between the diagnostic tool and the vehicle. A wired Ethernet cable (RJ45) or USB-to-Ethernet adapter connects the diagnostic tester (ex CANoe) directly to the Vehicle Communication Interface (VCI) or the ECU gateway. This method allows the diagnostic tester to access the vehicle’s ECUs without additional routing or address translation. This results in a low latency and high data transfer speeds.
This type of connection is usually used in workshop or testing environments where a physical connection is feasible and reliable. Option 1 is preferred for engineering diagnostics, flashing ECUs and in-depth vehicle analysis in a controlled setting.
DoIP Protocol connection types: Option 2 (Indirect Routed)
DoIP Option 2 enables an indirect routed connection (remote diagnostic access) by transmitting diagnostic messages through an IP router or gateway. Instead of a direct link, the diagnostic tool communicates with the vehicle remotely via an intermediate router (e.g. a central gateway or a cloud-based system). Option 2 requires an IP router that supports DoIP message forwarding.
This setup is beneficial for fleet management, remote diagnostics and over-the-air (OTA) updates, where a direct physical connection is not possible. However, Option 2 introduces additional network security challenges, requiring firewall configurations and message forwarding mechanisms to ensure safe communication.
Comparison: DoIP Option 1 vs Option 2
| Feature | Option 1 (Direct Connection) | Option 2 (Routed Connection) |
|---|---|---|
| Connection Type | Direct Ethernet (RJ45) | Routed via Network (Router/Gateway) |
| Latency | Low (fastest response time) | Higher due to routing delays |
| Security | More secure (direct access) | Requires firewall & security management |
| Use Case | Workshop diagnostics, ECU flashing | Remote diagnostics, fleet management, OTA updates, cloud-based diagnostic |
Final Thoughts
Both DoIP Protocol Option 1 and Option 2 serve different purposes in vehicle diagnostics. Option 1 is best for local diagnostics with high speed and reliability where a physical connection is possible with the ECUs. Whereas, Option 2 allows remote diagnostics and access, making it useful for cloud-based diagnostics. When vehicle is away from the engineer then Option 2 is useful.
Both options are part of the DoIP standard and are used depending on the specific requirements of the diagnostic task and the available infrastructure.
