CAN FD

Classic CAN hits a physical wall: arbitration relies on every node seeing the same bit at the same moment, which caps speed at around 1 Mbit/s depending on cable length. Bosch's 2012 answer was to go slow only when it matters. Arbitration runs at the old rate; once a node has won the bus it switches up, typically to 2–5 Mbit/s, for the data field and drops back before the acknowledgement.

The payload grew from 8 to 64 bytes at the same time, which makes it practical to reflash a car's ECUs over the bus and to bolt on message authentication. The original version had a weakness in its CRC protection that was fixed when the protocol was standardised in ISO 11898-1:2015 — with the result that "ISO CAN FD" and "non-ISO CAN FD" don't talk to each other. The next step, CAN XL, pushes payloads to 2048 bytes.