What is short message service center (SMSC)?
The short message service center (SMSC) is the portion of a mobile phone network that handles text message operations. It is responsible for receiving, storing, routing and forwarding SMS messages from mobile handsets. It is also referred to as a short message service -- service center (SMS-SC).
One or more SMSCs are involved with all text (SMS) messages. In a typical message flow, the message is sent by the handset to the SMSC. The SMSC responds to the handset with a small message indicating it accepted the SMS. If the recipient is not in the same network, it forwards it to the correct network's SMSC. The SMSC then determines if the recipient handset is available to receive the SMS. If it is not available, the SMSC will store the message. When the recipient is online it will send the message.
The SMSC works with the other components of a mobile network to determine if the recipient is online. This includes the home location register (HLR), the visitor location register (VLR) and the mobile switching center (MSC).
The SMSC will also work with SMS gateways. SMS gateways allow text messages to travel between networks and into different applications. For example, this allows SMS messages to be sent and received by email or to be automatically sent by programs. This also allows SMS to be integrated into line of business (LOB) applications.
The SMSC also determines the validity period to store the message. The sending handset can tell the SMSC how long to store the message. This is an optional request, and the retention policy is set by the carrier configuration and enforced by the SMSC and may be different. Once the validity period is past, if it is unable to successfully send the message, the SMSC will delete the stored message.
Short message service Center address
Each SMSC has an address identifying it on the network. The SMSC address is the same format as an international standard phone number. The SMSC address is part of the mobile network provider's configuration and is included on the SIM card or in the network provisioning package when the phone is initialized. Typically, the end user should not need to set the SMSC used by the handset.
SMSC on Android and iOS
Users can view their SMSC on an Android device but can no longer do so an iOS device. Apple users can see if their SMSC requires updating, however.
SMSC in Android
To view an SMSC on an Android device:
- Open the Phone
- Dial *#*#4636#*#* to open the Testing menu.
- Tap Phone Information.
- Scroll to the bottom to the entry for SMSC.
- Tap Refresh to load the current SMSC Number.
SMSC in Apple iOS
To update the SMSC on an Apple iOS device, open the settings application when on Wi-Fi or connected to the carrier's cellular network. Navigate to General, then About. If an update is needed, users will see a prompt to update the carrier settings.
Previously iOS users could see their SMSC in a manner similar to Android using the following steps:
- Open the Phone
- Dial *#5005*7672# then tap Call.
- The current SMSC number will be shown.
This process now results in an error message.
SMSCs are part of a mobile network's infrastructure and are therefore highly secured, but they are still open to several types of attack. The SMSC address is open and known. This allows for the possibility of spoofing SMS messages, sending SMS spam messages without being charged and denial of service (DOS) attacks through message flooding.
SMS data may be transmitted and stored on the SMSC in plain text. End users should be aware that SMS messages may be intercepted and read.
The future of SMSC
The SMSC will remain a vital part of mobile networks for the foreseeable future. Average users are sending less SMS messages to each other, person to person, compared to years past; instead, they are using alternative apps that do not use SMS, such as iMessage, WhatsApp and Signal.
Despite this, the overall use of SMS has not decreased significantly due to the increase of application-to-person messages. This includes the use of one-time passwords (OTP) and for two-factor authentication and other purposes, delivery text notifications and automated real-time alerts, all of which can be sent though SMS messages.