A Practical Message ID Assignment Policy for Controller Area Network that Maximizes Extensibility

Controller Area Network (CAN) is widely used in automotive applications. Policies for message ID and thus priority assignment have a significant impact on schedulability. In addition, they also determine extensibility; the scope to add messages required by future upgrades without compromising schedulability. In this paper we address message ID assignment, such that the system is extensible. First, we provide an assessment metric that provides an in-depth view of the extensibility of a given ID-assignment, tailored for use in automotive applications. Second, we develop a practical ID assignment policy which maximizes extensibility. This policy provides an upgrade pathway: it is used to provide the initial ID-assignment, and also used for ID-assignments during subsequent upgrades. The policy optimizes extensibility by maintaining Deadline minus Jitter Monotonic Priority Ordering, which ensures that it does not compromise either schedulability or robustness to errors on the bus. Evaluation using a simple automotive benchmark shows the effectiveness of the policy over multiple upgrades.