CAN was designed by Bosch and is currently described by ISO 11898. In terms of the Open Systems Interconnection model (OSI), CAN partially defines the services for layer 1 (physical) and layer 2 (data link). Other standards such as DeviceNet, Smart Distributed System, CAL, CAN Kingdom and CANopen (collectively called higher layer protocols) build upon the basic CAN specification and define additional services of the seven layer OSI model. Since all of these protocols utilize CAN integrated circuits, they all comply with the data link layer defined by CAN.
Device level networks such as DeviceNet and Smart Distributed System are low-level networks that provide connections between simple industrial devices such as sensors and actuators and higher- level devices such as controllers. Benefits of device level networks include reduced wiring costs, the ability to exploit the intelligence present in some low-level devices and improved diagnostic capabilities from that of hard-wired systems.
White Paper: Ethernet, ARCNET, CAN - Proposed Network Hierarchy for Open Control
When we discuss control strategy, the issue of networks is always raised. Since network requirements vary depending upon the complexity of control, different network technologies are usually specified for the various levels of control hierarchy. It is common to identify three different networks when describing a control system. The lowest level is the device network that is used to link sensors and actuators to controllers. Above that is the control level that links the various controllers together. The highest level is the information level used to link the control system to the enterprise-wide information system. With the movement toward open control systems, it is only logical to pick three open networking standards to complete the control system networking hierarchy. What is recommended here is Ethernet for the information network, ARCNET for the control network and CAN for the device network.