Content for  TS 23.040  Word version:  18.0.0

The Short Message Relay Layer (SM-RL) provides a service to the Short Message Transfer Layer (SM-TL). This service enables the SM-TL to send Transfer Protocol Data Units (TPDUs) to its peer entity, receive TPDUs from its peer entity and receive reports about earlier requests for TPDUs to be transferred. In order to keep track of TPDUs and reports about those TPDUs, primitives between the SM-TL and SM-RL contain a Short Message Identifier (SMI), which is a reference number for the TPDU associated with the primitive. This Short Message Identifier is not carried via the SM-RL protocol of clause 9.3.2. It is carried via the relay layer service between the SC and GMSC. It is also carried by SM-RL of TS 24.011, between the visited MSC and MS. The parameter is not carried by MAP but is mapped to and from the TCAP dialogue Identifier (see CCITT Recommendation Q.771, "Blue Book" [19]) at the GMSC and the visited MSC (therefore the Message Identifier at the SC/GMSC interface is not the same as at the visited MSC/MS interface). The SM-RL communicates with its peer entity by the protocol described in the following clauses.

Different protocols are required between different pairs of SM-RL entities. Those are described in other GSM/UMTS specifications. This clause gives a survey of the different information elements which have to be conveyed between those entities. (Note that the notation of the protocol and information elements may vary between different GSM/UMTS specifications). The SM-RL comprises the following 6 protocol elements: