Communications

The Communications View identifies the protocol stacks needed to implement an information flow between a source and destination (e.g., information flow triple) in the Physical View. ARC-IT terms these protocol stacks as "solutions". Solutions are composed of a collection of industry standards; usually formally developed standards produced by a standards development organization, but often a published specification such as an IETF RFC. Each triple from the Physical View is associated with one or more solutions. These solutions, their components and attributes can be examined from several different perspectives and from different places within ARC-IT.

A typical triple solution is assembled according to the ARC-IT communications model, as defined by the communications viewpoint. All solutions are built according to this model, and the components of the solution assigned to the various parts of the model depending on their role in the solution. Sometimes a standard satisfies multiple aspects of a solution, and so might appear more than once in an illustration of the solution. Triple solutions are accessible from several places, but are most commonly from the context of a service package by clicking on the flow or from the overall list of ARC-IT triples.

A sample triple solution is shown at right. Standards names are sometimes hyperlinked: this indicates the standard is actually part of a group of standards or one of several alternatives; clicking on the link will expand the bundle or explain the alternatives. 'Info' buttons next to standards generate pop-ups that provide some detail about the standard in question.

There are also several 'gap' icons on this image. These reflect issues with the use of standards in that particular area of the model. Issues come in two types: gaps, which are issues where some requirement of the triple is not met by the standard or collection of standards in the solution, or overlaps, which are issues where multiple standards exist to serve the solution, and it is not obvious which one to choose. Issues are also assigned severity levels, which indicate the degree to which the issue impacts the operation of the solution in practice. On the example to the right there is a moderate-level security gap and a minor gap at the ITS Application Entity. Note that some layers might have alternatives, in which case all of the gap icons associated with every alternative may be shown on the diagram, but the solution severity calculations (and resulting ordering of solutions) includes only the issues associated with the default (i.e., best, least severe) alternative.

To assist with the management of the communications model and the vast amount of assignments within ARC-IT, an intermediate construct called a profile is used. Generally, the communications profile provides management, security and exchange of data between devices, while the data profile defines the data elements, message, dialogs and defines mechanisms for managing and securing at the ITS Application Entity.

The ARC-IT Communications View defines dozens of communications profiles that support all links defined in the physical view. These links are commonly abbreviated as n2m, where n and m are one of C (Center or Support), I or F (Field), V (Vehicle), P (Traveler, or Personal). So V2V names the link between vehicles, while C2F names the link between center and field infrastructure. Similarly, ARC-IT defines many more data profiles that accommodate the data needs of all associated triples.

Further details behind the development of the communications view are described in the communications viewpoint page.