The CAN communication protocol is a carrier-sense multiple-access protocol with collision detection and arbitration on message priority (CSMA/CD+AMP). CSMA means that each node on a bus must wait for a prescribed period of inactivity before attempting to send a message.

CD+AMP means that collisions are resolved through a bit-wise arbitration, based upon a preprogrammed priority of each message in the identifier field of a message. The higher priority identifier always wins bus access.

The first version of the CAN standards listed in Table 1, ISO 11519 (Low-Speed CAN) is for applications up to 125 kbps with a standard 11-bit identifier.

The second version, ISO 11898 (1993), also with 11-bit identifiers provides for signaling rates from 125 kbps to 1 Mbps while the more recent ISO 11898 amendment (1995) introduces the extended 29-bit identifier.

The ISO 11898 11-bit version is often referred to as Standard CAN Version 2.0A, while the ISO 11898 amendment is referred to as Extended CAN Version 2.0B. The Standard CAN 11-bit identifier field in Figure 2 provides for 211, or 2048 different message identifiers, while the Extended CAN 29-bit identifier in Figure 3 provides for 229, or 537 million identifiers.