This GTS describes the point-to-point Short Message Service (SMS) of the GSM PLMN system. It defines: - the services and service elements; - the network architecture; - the Service Centre functionality; - the MSC functionality (with regard to the SMS); - the routing requirements, - the protocols and protocol layering; for the Teleservices 21 and 22, as specified in the GSM 02.03 (ETS 300 502). The use of radio resources for the transfer of short messages between the MS and the MSC is described in GSM 04.11 (ETS 300 559) Point-to-Point Short Message Service Support on Mobile Radio Interface , and is dealt with in that specification. The network aspects of Short Message Service provision are outside the scope of this specification (i.e. the provision of network connectivity between the PLMN subsystems). The required and assumed network service offered to the higher layers is defined in this specification. The Cell Broadcast Short Message Service (Teleservice 23) is a separate service, and is described in GSM 03.41 (ETS 300 537) Technical Realization of the Short Message Service - Cell Broadcast .