Hello guys, welcome back to our blog. In this article, I will discuss how is DoIP different from CAN-based diagnostics, the advantages of DoIP over CAN-based diagnostics, and the future of DoIP.

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How Is DoIP Different From CAN-based Diagnostics

The automotive industry is undergoing a seismic shift with the growing adoption of advanced driver assistance systems (ADAS), autonomous driving, electrification, and vehicle-to-everything (V2X) technologies. With these advancements comes an exponential increase in Electronic Control Units (ECUs), sensors, and software modules integrated into modern vehicles.

Amidst this digital revolution, automotive diagnostics play a pivotal role. Vehicle diagnostics ensure that these high-tech systems function as intended, helping engineers and service technicians identify, troubleshoot, and fix issues before they escalate. Traditionally, diagnostics were carried out using the Controller Area Network (CAN) protocol. However, in recent years, Diagnostics over Internet Protocol (DoIP) has emerged as a powerful alternative.

This article provides a comprehensive breakdown of DoIP vs. CAN-based diagnostics, exploring their architecture, performance, use cases, and future relevance in the software-defined vehicle era.

🚙 What is CAN-based Diagnostics?

CAN (Controller Area Network) is a multi-master, message-oriented protocol introduced by Bosch in 1986, and it’s been the backbone of in-vehicle communication ever since. It allows microcontrollers and devices to communicate with each other without a host computer. This makes it ideal for automotive applications where multiple ECUs need to exchange data quickly and efficiently.

🔍 Diagnostics Using CAN

Diagnostics over CAN primarily use the Unified Diagnostic Services (UDS) protocol defined in ISO 14229. In UDS over CAN, messages are transmitted using CAN frames, typically with 8 bytes per frame and a maximum speed of 1 Mbps (Classical CAN) or up to 5 Mbps (CAN FD).

Common UDS services over CAN include:

Reading and clearing Diagnostic Trouble Codes (DTCs)
ECU identification
Flash programming (reprogramming ECUs)
Security access and authentication
Sensor and actuator tests

🌐 What is DoIP?

DoIP (Diagnostics over Internet Protocol) is a diagnostic communication protocol specified in ISO 13400, built on standard TCP/IP and Ethernet technologies. It offers a high-speed, flexible, and scalable alternative to traditional diagnostic communication methods.

🚀 Key Layers in DoIP

Application Layer: UDS (same as CAN-based diagnostics)
Transport & Network Layers: TCP/IP, UDP/IP
Data Link & Physical Layers: Ethernet (100BASE-TX or 1000BASE-T)

With Ethernet speeds ranging from 100 Mbps to 1 Gbps or higher, DoIP is tailor-made for modern, connected vehicles with massive data transfer needs.

CAN Vs DoIP: Side-by-Side Comparison

Feature	CAN-based Diagnostics	DoIP-based Diagnostics
Protocol	ISO 14229 over ISO 11898	ISO 14229 over ISO 13400
Physical Layer	CAN (2-wire, differential)	Ethernet (twisted pair or optical)
Data Rate	1 Mbps (CAN), up to 5 Mbps (CAN FD)	100 Mbps, 1 Gbps or higher
Frame Size	8 bytes (Classical CAN), up to 64 bytes (CAN FD)	~1500 bytes (standard Ethernet frame)
Topology	Bus topology	Star topology (switched network)
Use Case	In-vehicle ECU communication and diagnostics	Remote diagnostics, over-the-air updates, and production line
Bandwidth	Low	High
IP-based Communication	❌	✅
Security Support	Limited	Advanced (TLS, IPsec possible)

📡 Advantages of DoIP over CAN-Based Diagnostics

⚡ 1. Higher Data Bandwidth

DoIP supports much larger payload sizes and higher speeds. This is crucial for:

Flashing large software images to ECUs
Remote diagnostics and updates
Event data transfer (logs, crash data)

🌍 2. Remote Diagnostics

CAN requires physical proximity and a direct connection to the vehicle’s diagnostic port (OBD-II or manufacturer-specific). With DoIP, diagnostics can be performed remotely using IP networks.

Example: An OEM can run diagnostics on a vehicle sitting at a dealership from their central R&D lab using DoIP.

🧩 3. Scalability

Ethernet networks can scale easily by adding switches and IP addressing, unlike CAN buses, which have physical limitations in terms of node count and length.

🔐 4. Enhanced Security

CAN lacks built-in security features. DoIP can leverage standard IT security protocols like:

Authentication
IP whitelisting
Encrypted communication (TLS)

This is especially important in connected and autonomous vehicles.

🔧 5. Multi-Node Parallel Diagnostics

DoIP allows diagnostics across multiple ECUs at the same time using IP addressing. On CAN, communication is limited to one diagnostic session at a time.

🚗 When to Use CAN-Based Diagnostics

Despite DoIP’s advantages, CAN is still heavily used in scenarios such as:

Low-cost vehicles
Simpler ECUs like window or seat controllers
Real-time low-latency communication between ECUs
Vehicles without an Ethernet backbone

🌐 When to Use DoIP

DoIP becomes the preferred option in:

Electric vehicles (EVs) and high-end cars
Over-the-air (OTA) updates
Big software/data flashing on ECUs
Production line testing and diagnostics
Telematics units with remote vehicle access

🛠️ Diagnostic Use Cases Comparison

Use Case	CAN	DoIP
Read DTCs	✅	✅
Flash ECU software	✅ (limited speed)	✅ (faster)
Remote diagnostics	❌	✅
Simultaneous ECU testing	❌	✅
Security support	Limited	Strong
OTA updates	❌	✅

🏗️ Implementation Challenges in DoIP

While DoIP offers modern benefits, its implementation poses challenges:

Requires Ethernet architecture in the vehicle
Higher complexity in diagnostic tools
Additional training for technicians
Secure gateway configurations

To address these, OEMs are adopting centralized gateways and zonal architecture that combine both CAN and Ethernet to ensure a seamless transition.

🛡️ Role of Secure Gateways

Secure gateways in modern ECUs manage access control between external diagnostic testers and in-vehicle networks. In a DoIP setup, they:

Validate diagnostic requests
Route allowed traffic to ECUs
Prevent unauthorized access

This ensures that only authenticated diagnostic testers can perform sensitive actions like flashing or clearing DTCs.

📈 Future Outlook: DoIP and Beyond

💡 Software-Defined Vehicles (SDVs)

As vehicles become SDVs, frequent software updates will be required. DoIP enables this by allowing:

High-speed data transfer
Cloud integration
Predictive maintenance

🚀 Integration with Cloud Platforms

Cloud-connected diagnostic tools can communicate with the car over a VPN or encrypted tunnel using DoIP, opening the door for:

Predictive diagnostics
Big data analytics
Continuous software deployment

🔗 Combined Use with CAN and FlexRay

In many architectures, DoIP is used for diagnostics while CAN remains the backbone for real-time communication between ECUs. FlexRay or Automotive Ethernet may also be used for time-critical tasks.

🔚 Conclusion

The evolution from CAN to DoIP represents a major leap in automotive diagnostics. While CAN-based diagnostics have served the industry for decades, the increasing software content in vehicles demands a more robust, high-speed, and connected solution, and DoIP fits the bill.

Both protocols will coexist in many vehicles. CAN will remain vital for real-time in-vehicle communication, while DoIP will dominate the diagnostic landscape, particularly for connected, electrified, and autonomous vehicles.

If you are a diagnostics engineer, embedded systems developer, or working on next-generation ECUs, understanding both CAN and DoIP is essential. The future is hybrid, blending the best of both protocols.

✍️ About the Author

Chetan Shidling is an Automotive Software Engineer with hands-on experience in diagnostics, HiL testing, Simulink, and ECU development. He shares in-depth tutorials and insights on LinkedIn and YouTube on embedded systems, automotive tools, and technologies shaping the mobility ecosystem.

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