GSM 03.40

GSM 03.40 or 3GPP TS 23.040 is a mobile telephony standard describing the format of the Transfer Protocol Data Units (TPDU) of the Short Message Transfer Protocol (SM-TP) used in the GSM networks to carry Short Messages. This format is used throughout the whole transfer of the message in the GSM mobile network. In contrast, application servers use different protocols, like Short Message Peer-to-Peer or Universal Computer Protocol, to exchange messages between them and the Short Message Service Center (SMSC).

GSM 03.40 is the original name of the standard. Since 1999 has been developed by the 3GPP under the name 3GPP TS 23.040. However, the original name is often used to refer even to the 3GPP document.