SMS stands for short messaging service, it refers to a protocol that is used for sending short messages over wireless networks.
SMS works on the fundamental principle voice network, and is based on the three big technologies (i.e. GSM, CDMA and TDMA) which makes it a universal service.
Step-by-step explanation:
Data SMS messages are sent through the data network, using the 2G / 3G/4G data connection.
A perfect example for data SMS use is when your recipient has pay to receive the text message even though they may have unlimited texting. By using a data SMS service, all extra charges are avoided and the amount of data used by SMS messages is insignificant compared to even lite web page viewing.
Data SMS messages are sent not only through the data network (over your 2G / 3G data connection), but also through GSM as Text SMS.
The PDU of a text message has a User Data Headers (UDH) that defines a specific port on a handset