The Short Message Service (SMS) provides a means of sending messages of limited size to and from GSM/UMTS/EPS
mobiles. The provision of SMS makes use of a Service Centre, which acts as a store and forward centre for short
messages. Thus a GSM/UMTS/EPS PLMN needs to support the transfer of short messages between Service Centres
Mobile originated messages shall be transported from an MS to a Service Centre. These may be destined for other
mobile users, or for subscribers on a fixed network. Mobile terminated messages shall be transported from a Service
Centre to an MS. These may be input to the Service Centre by other mobile users (via a mobile originated short
message) or by a variety of other sources, e.g. speech, telex, or facsimile.