SMS

SMS stands for Short Message Service and is a text messaging service built into cellular networks to exchange short alphanumeric messages between mobile devices. It originated within GSM networks in the 1980s and was standardized by the ETSI/3GPP family. Messages are handled by a centralized element called the Short Message Service Center (SMSC), which stores, forwards, and, if necessary, retries delivery when the recipient becomes reachable again. Delivery reports may be generated to indicate success, pending, or failure.

A single SMS typically uses a 7-bit default alphabet and can carry up to 160 characters. For messages that require broader character sets, such as many non-Latin scripts, UCS-2 encoding reduces the limit to about 70 characters. When messages exceed these limits, they can be split and reassembled as concatenated SMS, with typical per-part payloads of 153 characters for 7-bit and 67 characters for UCS-2, depending on the encoding and network support.

SMS messages traverse operator networks using signaling paths or interconnect protocols. The SMSC communicates with the originating and destination networks and, in many cases, with third-party applications via protocols such as SMPP. Some configurations enable delivery over IP networks as well.

History and impact: the first SMS was sent in 1992, and the service rapidly became widespread in the late 1990s and 2000s, becoming a common channel for person-to-person communication, as well as alerts, notifications, and two-factor authentication.

Limitations include limited security and privacy, lack of guaranteed end-to-end encryption, dependence on network availability, and potential costs. SMS faces competition from messaging apps that support richer media and end-to-end encryption.