Bearer services are data transport services offered by the operating companies. These services always refer to the functions of the lower three layers of the OSI reference model. The user can use this service for transparent information transmission to his communication partner.
Bearer services can be classified according to the technical features and usage aspects. In terms of technical features, a distinction is made between dial-up lines and leased lines; in terms of usage aspects, a distinction is made according to characteristic network features. For example, DTAG's services may be based on the analog public switched telephone network (POTS), IDN or ISDN, standard leased lines or monopoly transmission paths.
GSM networks provide their bearer services to subscribers exclusively as a circuit-switched service, exclusively for a selected end-to-end connection, for the duration of the connection. For data transmission, the GSM network provides different transmission speeds of 300 bit/s, 1,200 bit/s, 2,400 bit/s, 4,800 bit/s and 9,600 bit/s. Synchronous transmissions and asynchronous transmissions are provided. Synchronous trans missions and asynchronous transmissions are supported, as well as analog transmissions and digital transmissions with secured protocols.