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 communication network ensures the secure transport of telecommunication and data communication services. The communication in such systems depends on the mediation and control of the traffic flow, which can be prioritized by the service
. These mechanisms favour, for example, traffic flows with a real-time character over others with a bursty character. The services offered in communication systems can be provided by external providers, but they can also come from other communication partners.