A communication system is reflected in the communication models such as the OSI reference model or other proprietary layer models. There is a clear separation between communication network and communication service.
A communication system can therefore be described as a communication network via which communication services are transmitted and made available to the user. The communications network ensures the secure transport of telecommunication and data communication services. Communication in such systems depends on the mediation and control of the traffic flow, which can be prioritized by the service. These mechanisms favor, for example, traffic flows of a real-time nature over others of a bursty nature.
The services offered in communication systems can be provided by external providers, but they can equally come from other communication partners.