Short message service center(SMSC)

A short message service center (SMSC) is a network element in the mobile telephone network. Its purpose is to store, forward, convert and deliver SMS messages.
The full designation of an SMSC according to 3GPP is Short Message Service - Service Centre (SMS-SC)
Basic Trajectories of SMS are

1. From Mobile to another Mobile, this trajectory is referred as MO-MT (Mobile Originated - Mobile Terminated)
2. From Mobile to a content provider (also called as Large Account / ESME), this trajectory is referred as MO-AT (Mobile Originated - Application Terminated)
3. From Application to a Mobile, this trajectory is referred as AO-MT (Application Originated - Mobile Terminated)

An SMS center (SMSC) is responsible for handling the SMS operations of a wireless network.

1. When an SMS message is sent from a mobile phone, it will reach an SMS center first.
2. The SMS center then forwards the SMS message towards the destination.
3. The main duty of an SMSC is to route SMS messages and regulate the process. If the recipient is unavailable (for example, when the mobile phone is switched off), the SMSC will store the SMS message.
4. It will forward the SMS message when the recipient is available or when the message's expiry period is exceeded.