CAN vs Ethernet | Difference between CAN and Ethernet
This page compares CAN vs Ethernet and mentions difference between CAN and Ethernet in automotive domain.
Introduction : Both CAN and Ethernet are communication protocols widely used in the automotive and industrial domains. CAN is commonly employed for real-time and safety-critical systems where as Ethernet is often utilized for non-real-time applications. Both CAN and Ethernet support various network topologies. Both the protocols facilitate the transmission of data packets or frames. They define the structure and formatting of these packets or frames which include headers, payload and error detection mechanisms. Both CAN and Ethernet have evolved over time to meet the changing requirements of the automotive and industrial sectors. Newer versions and enhancements, such as CAN FD (Flexible Data Rate) and Ethernet based protocols like Automotive Ethernet have been developed to address increased data rates, bandwidth and scalability requirements.
What is CAN ?
CAN (Controller Area Network) bus interface has undergone several evolutions and standardizations over time. These are as follows.
CAN 2.0 : This protocol version was introduced in 1991 as ISO 11898-1. It supports max. data rate of 1 Mbps. It supports both standard CAN and extended CAN message formats.
CAN FD : It was introduced to support high data rate requirements. It is backward compatible with CAN 2.0.
It increases max. frame payload from 8 bytes to 64 bytes to support efficient data transfer.
It is used in driver assistance systems and vehicle diagnostics testing.
CANopen : It provides communication and device management services. It allows interoperability between different devices across various manufactures.
CiA (CAN in Automation) : This non-profit association promotes and supports use of CAN protocols. It has developed CiA 402 for CAN based motion control
systems and CiA 447 for CAN based lift control systems.
Standard CAN frame and extended CAN frame fields are shown above. Refer Standard CAN vs Extended CAN >> for description of each of the fields used in these frame formats. CAN is widely used in various applications such as automotive and industrial applications, robotics, medical devices, building automation etc.
What is Ethernet ?
Ethernet is widely used in networking technology. It has evolved significantly since its adoption.
Following are the ethernet standards.
Ethernet (IEEE 802.3) : It defines Ethernet specifications which supports 10 Mbps data rate using coaxial cables
and CSMA/CD media access control method.
Fast Ethernet (IEEE 802.3u) : It supports 100 Mbps data rate. It supports twisted pair and fiber optic cables.
Gigabit Ethernet (IEEE 802.3z, IEEE 802.3ab) : It supports 1 Gbps data rates. It utilizes both fiber optic and twisted pair cables.
10 Gigabit Ethernet (IEEE 802.3ae) : It supports 10 Gbps primarily using fiber optic cables.
Ethernet in the First Mile or last Mile (IEEE 802.3ah, 802.3av) : These standards focuses on Ethernet access technologies
such as Ethernet over copper or PON etc.
Automotive Ethernet (IEEE 802.3bw, 802.3bp, 802.3cg) : These standards are focused on use of ethernet for in-vehicle communication which
enables higher data rates (~ 100 Mbps and 1 Gbps) over single or multiple twisted pairs.
As shown, Ethernet frame consists of preamble, Start Frame Delimiter (SFD), destination and source addresses, length, data and FCS fields. Refer Ethernet tutorial >> for more information. Ethernet is used in various applications such as LANs, WANs, industrial automation, internet connectivity, video surveillance and data centers. It is continuously evolving which has made it de-facto standard for wired networking in various industries and applications.
Difference between CAN and Ethernet
Both CAN and Ethernet provide communication solutions but they differ in terms of data rate, topology, distance coverage, communication mechanism, latency, error detection capability, interference resistance, cost etc. Following table mentions difference between CAN and Ethernet with respect to these parameters.
| Parameters | CAN | Ethernet |
|---|---|---|
| Communication | Designed and developed to support short range communication within a vehicle | Designed for local area network (LAN) communication, being used in automotive domain too. |
| Transmission mediums | Twisted pair wiring | Twisted pair or fiber optic cables |
| Bandwidth | Limited bandwidth compare to Ethernet | Higher |
| Data rate | Up to 1 Mbps (Typically) | From 10 Mbps to Multiple Gbps (Typically) |
| Topology | Bus based topology | Supports Bus, Star, Ring or Mesh topologies |
| Coverage distance | Up to few hundred meters | Up to several Kilometers (depending upon medium used) |
| Message length | Limited, up to 8 bytes (Standard CAN) or Up to 64 bytes (CAN FD) | Larger, up to 1500 bytes ethernet frame |
| Message Priority | Uses prioritized message IDs for arbitration | Does not have inherent message priority mechanism |
| Latency | Lower | Lower than CAN |
| Error detection | Built-in | Relies on TCP/IP for error detection and recovery |
| Security | Lacks in built-in security features | Support security protocols and encryption methods. |
| Interference | Resistant to EMI (Electromagnetic Interference) | Susceptible to EMI and hence requires appropriate shielding and grounding |
| Cost | Relatively lower cost compared to ethernet | Higher than CAN, cost varies based on implementation and requirements |
| Flexibility | Limited flexibility for integration with other networks | Offers greater flexibility for integration with various protocols and networks |
| Application | Widely used in automotive systems such as ECUs, sensors for real time and safety critical applications | Commonly used for infotainment, diagnostics and non-critical applications, being explored for automotive systems also |
| Standard specifications | Bosch CAN version 2.0 (1991, 1997), Bosch CAN-FD version 1.0 (2012), ISO-11898-1 standard (2015) | IEEE 802.3-2012 standard for ethernet |
Conclusion: As mentioned, both CAN and Ethernet have their respective strengths. They are suitable for different applications within the automotive domain. CAN is preferred for its reliability, determinism, and suitability for real-time and safety-critical systems. Ethernet offers higher data rates, broader bandwidth(BW) and compatibility with other network protocols. Hence Ethernet is preferred for non real time applications, infotainment and diagnostics in vehicles. The choice between CAN vs. Ethernet depends on these specific requirements and presence of other existing network infrastructure.