MSISDN

MSISDN stands for Mobile Station International Subscriber Directory Number. It is the telephone number, including country code, assigned to a mobile phone subscriber. In essence, it is the number that allows the mobile network to identify and route calls and messages to a specific mobile device. The MSISDN is a crucial element in the Global System for Mobile Communications (GSM) and other mobile networks like UMTS and LTE.

The structure of an MSISDN follows international dialing conventions. It begins with a country code, followed by a national destination code, and finally the subscriber number. For example, in North America, the country code is 1, followed by a three-digit area code, and then a seven-digit subscriber number. This hierarchical structure ensures that calls can be routed correctly across different countries and within a national network.

While the MSISDN is the public-facing identifier for a mobile subscriber, it is distinct from the International Mobile Subscriber Identity (IMSI). The IMSI is a unique number associated with the subscriber's SIM card and is used internally by the network for identification and authentication purposes. The MSISDN is what other people dial to reach a mobile phone, whereas the IMSI is used by the network to manage the subscriber's connection and services.