How is J1939 different from NMEA 2000?

J1939 and NMEA 2000 networks are both based on the same hardware (Controller Area Network (CAN)), and both protocols use the same message format (the messages are actually compatible and can coexist on the same network), however, NMEA uses different messages from J1939 for most parameters. The other main difference between the two networks has to do with addressing. In J1939, manufacturers "hard code" the node address for each product connected to the network, whereas NMEA 2000 products negotiate and resolve their node addresses automatically when they are plugged into a network, making NMEA 2000 "plug-and-play" as opposed to J1939, which requires manual intervention whenever a new product is connected to a J1939 network.