23.0403GPPRelease 17Technical realization of the Short Message Service (SMS)TS
The Short Message Transfer Layer (SM‑TL) provides a service to the Short Message Application Layer (SM‑AL). This service enables the SM‑AL to transfer short messages to its peer entity, receive short messages from its peer entity and receive reports about earlier requests for short messages to be transferred.
In order to keep track of messages and reports about those messages, primitives between the SM‑AL and SM‑TL contain a Short Message Identifier (SMI), which is a reference number for the message associated with the primitive. This Short Message Identifier is mapped to and from the Short Message Identifier used between the SM‑TL and the Short Message Relay Layer (SM‑RL). The Short Message Identifier is not carried between entities and therefore a given message may have different SMIs at the MS and SC sides (see clause 9.3.1 below).
The SM‑TL communicates with its peer entity by the protocol described in the following clauses.