CAN Bus vs. DoIP
Comparing 2 standards across 13 specifications. 13 key differences identified.
Controller Area Network (CAN Bus, invented by Robert Bosch GmbH in 1986 and standardized under ISO 11898) is the multi-master, message-broadcast serial bus governing electronic control units (ECUs). Operating at 500 kbps (High-Speed CAN) over a twisted pair with 120-ohm termination resistors, utilizing differential voltage signaling (CAN_H / CAN_L) and non-destructive bitwise arbitration.
Diagnostics over Internet Protocol (DoIP, standardized under ISO 13400) replaces slow serial buses with high-speed Automotive Ethernet (100BASE-TX, 100BASE-T1, 1000BASE-T1) using standard TCP/IP and UDP protocols. Operating over TCP Port 13400, it accelerates ECU firmware reflashing and over-the-air (OTA) software updates by up to 100× compared to legacy CAN bus.
Specification Comparison Table
13 Parameters| Parameter / Spec | ||
|---|---|---|
|
Standardization
|
ISO 11898-2 (High-Speed physical medium) / SAE J2284 | ISO 13400-2:2019 (Transport protocol and network layer services) |
|
Transmission Speed
|
500 kbps standard for powertrain (Engine, Transmission, ABS, Airbag); 125-250 kbps for body electronics | — |
|
Differential Voltage Levels
|
Recessive state (Logic 1): CAN_H = 2.5V, CAN_L = 2.5V (Diff = 0V) | Dominant state (Logic 0): CAN_H = 3.5V, CAN_L = 1.5V (Diff = 2.0V) | — |
|
Bus Termination
|
Exactly two 120 Ω terminating resistors at opposite physical ends of the bus (total measured resistance between CAN_H & CAN_L = 60.0 Ω) | — |
|
Frame Format (CAN 2.0B)
|
11-bit standard identifier or 29-bit extended identifier with up to 8 data payload bytes | — |
|
Bitwise Arbitration
|
Dominant zero bits overwrite recessive one bits; the lowest numerical CAN ID has the highest priority and never loses arbitration | — |
|
Fault Confinement
|
Hardware error counters automatically transition faulty nodes from Error-Active -> Error-Passive -> Bus-Off isolation | — |
|
Physical Layer
|
— | 100BASE-TX (Standard twisted-pair Ethernet) or 100BASE-T1 / 1000BASE-T1 (Single-pair Automotive Ethernet) |
|
Network Port
|
— | TCP Port 13400 (Diagnostic message transport) & UDP Port 13400 (Vehicle discovery and routing activation) |
|
OBD-II DLC Activation Pin
|
— | Pin 8 on OBD port is driven to +12V or pulled down to wake up the vehicle's DoIP Ethernet gateway |
|
Throughput Advantage
|
— | 100 Mbps to 1 Gbps throughput, roughly two to three orders of magnitude faster than 500 kbps CAN bus for large ECU firmware transfers |
|
Vehicle Identification Handshake
|
— | Vehicle Announcement Message broadcasts VIN (17 chars), Logical Address (2 bytes), and MAC address via UDP broadcast |
|
OEM Deployments
|
— | BMW (ENET cable / ISTA), Mercedes-Benz (Xentry DoIP), Volvo (VIDA), Porsche, modern VAG platform (ODIS) |