This part of ISO/TS 17575 defines how to convey all or parts of the data element structure defined in ISO/TS 17575-1 over any communication stack and media suitable for this application. It is focussed on mobile communication links. However, wired links shall use the same methodology. To establish a link to a sequence of service calls initializing the communication channel, addressing the reception of the message and forwarding the payload are required. The required communication medium independent services are part of the definition of this part of ISO/TS 17575, represented by an abstract API. The communication interface shall be implemented as an API in the programming environment of choice for the Front End (FE) system. The definition of this API in concrete terms is outside of the scope of this part of ISO/TS 17575. This part of ISO/TS 17575 specifies an abstract API that defines the semantics of the concrete API. An example concrete API is presented in Annex C. Where no distinction is made between the abstract and concrete communications APIs, the term “communications API” or just “API”, can be used.