MSISDN (Mobile Subscriber Integrated Services Digital Network number) is the term used to describe a mobile number in an international format. However, the MSISDN is not a direct mapping to a mobile handset, or even to the SIM card. An MSISDN allows an SMSC to determine the country and mobile operator a subscriber number belongs to; and from there the SMSC can query the mobile operator’s HLR (Home Location Register) for information used to route the SMS to the handset.
An SMS message sent from an application to a handset is referred to as a Mobile Terminating (MT) message. The term describes the process and flow of an application (software) sending a short message submission to an aggregator utilizing the SubmitSM transaction which will store and forward the message onto a terminating operator SMSC that is able to reach the destination mobile number. Once the message is delivered to the handset, a delivery notification is sent back to the aggregator and then the enterprise acknowledging delivery.