The OSEK standard comprises also an agreement on interfaces and protocols for in-vehicle communication called OSEK COM. The term in-vehicle communication means both communication between nodes and internal communication in a node of the whole vehicle. The basic idea is to provide a standardized API for software communication that is independed from the particular communication media used in a way to ease porting of applications between different hardwares.
The OSEK COM standard is composed by:
An Interaction layer which provides communication services for the transfer of application messages.
A Network layer which provides services for the unacknowledged and segmented transfer of application messages. The network layer provides flow control mechanisms to enable interfacing of communication peers featuring different level of performance and capabilities.
A Data link layer interface which provides services for the unacknowledged transfer of individual data packets over a network to the layers above.
OSEK COM provides a rich set of communication facilities but it is likely that many applications will only require a subset of this functionality. For that reason, the standard defines a set of conformance classes to enable the integration of OSEK COM in systems featuring various levels of capabilities in a scalable way, enabling the car producer to integrate software parts produced by different suppliers.
OSEK COM defines these levels as Communication Conformance Classes (CCCs). The main purpose of the conformance classes is to ensure that applications which have been for a particular conformance class are portable across different OSEK implementations and ECUs featuring that same or higher level of communication functionality. OSEK COM defines five communication conformance classes to provide support from ECU internal communication only (CCCA) up to inter-ECU external communication (CCC2).
For an OSEK implementation to be compliant, message handling for intra processor communication has to be offered. The minimum functionality required is CCCA as described in the OSEK COM specification.