Traffic on the CAN bus consists of five types of message frames. They are covered in detail in the part-2 introductory course. To illustrate how data flows on the bus, let's use a data frame, which carries actual data. When a transmitter at a CAN node sends a data frame, it broadcasts that message to all nodes on the bus. However, only those nodes configured to recieve the identifier message will accept and save the data. All other nodes do nothing with the data. CAN 2.0A has an 11-bit message identifier and was originally specified to operate at a maximum frequency of 250kbps. CAN 2.0B has 11-bit or 29-bit message identifiers and can be used at up to speeds of 1Mbps.