The Short Message Peer to Peer (SMPP) protocol is an open industry standard messaging protocol designed to simplify integration of data applications with wireless mobile networks such as GSM, TDMA, CDMA and PDC. The protocol is widely deployed in the mobile telecommunications industry. The SMPP protocol specification is freely available from the Documents section of this site. - from SMS Forum

The short message peer-to-peer protocol (SMPP) is a protocol for exchanging SMS messages between SMS peer entities such as short message service centres. It is often used to allow third parties (e.g. content suppliers like news organisations) to submit messages, often in bulk. -- SMPP