Short Message Peer-to-Peer (SMPP) is used in building SMS API integrations and is considered the industry-standard protocol for sending SMS to Network providers. Overall, the telecommunications industry uses SMPP for exchanging SMS between Short Message Service Centers (SMSC) and External Short Messaging Entities (ESME).
SMPP is a level-7 TCP/IP protocol, which allows fast delivery of SMS messages using the most common versions, v3.3 and v3.4, with the possibility of synchronous and asynchronous data exchange.