Using standardized transmission procedures and interfaces, the providers and carriers of the individual countries offer application-oriented services for message transmissionor communication on their transmission networks.
The services differ essentially in the features ofswitching technology and compatibility of network access. Switching technology is based on two methods. In circuit switching, a physical connection is provided between two subscribers, which is exclusively available to the connected subscribers. In partial circuit switching, on the other hand, there is no longer a physical connection between two subscribers, but only a logical or virtual connection.