What Happens When You Send an SMS? A Behind-the-Scenes Look at Text Messaging

What Happens When You Send a Text from Your Phone?

When you send an SMS text, your phone first encodes the message using GSM standards. It then sends the message to your carrier’s SMS Center (SMSC) via a nearby cell tower. The SMSC stores, routes, and forwards the message through the network to the recipient’s cell tower, where it’s delivered to their device. SMS can provide delivery receipts, but it doesn’t offer read receipts. This entire process happens in seconds, ensuring SMS is a fast and dependable messaging solution. Continue reading below to follow the exact path your message takes and the steps involved.

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How SMS Texts Are Delivered

Step 1: Typing and Sending the Message

The process begins the moment you type your message and hit send. Your mobile device formats the text using a standard encoding called the GSM 7 bit alphabet, which allows up to 160 characters in a single SMS segment. If your message exceeds this limit, it is split into multiple segments that will later be reassembled by the recipient’s device.

When you press send, your device does not communicate directly with the recipient’s phone. Instead, it transmits the message to the nearest cell tower using radio signals. This first step is where mobile networks convert your action into a format that can travel through the telecom infrastructure.

Step 2: Transmission to the SMS Center (SMSC)

Once the cell tower receives your message, it is forwarded to the SMSC, or Short Message Service Center. The SMSC is the central hub that manages the delivery of all SMS messages for a mobile carrier. Its responsibilities include storing the message temporarily, checking the recipient’s network availability, and ensuring the message is delivered as efficiently as possible.

If the recipient’s phone is unavailable, the SMSC will store the message and attempt delivery at regular intervals. This guarantees that messages are not lost, even if the recipient is out of coverage or has their phone turned off.

Step 3: Routing the Message

The SMSC determines the best path to reach the recipient. This can involve sending the message across multiple networks and routing systems, particularly if the sender and recipient are on different carriers or in different countries. The message travels through switches, gateways, and sometimes international routing hubs to reach the recipient’s SMSC or directly to their device, depending on the network configuration.

For MMS messages, a similar process occurs, but with additional handling for multimedia content. MMS messages are stored on the carrier’s multimedia server, and a notification is sent to the recipient to download the content using their mobile data connection.

Step 4: Delivery to the Recipient

Once the recipient’s device is reachable, the SMSC forwards the message to their cell tower. The cell tower sends the message over the air to the recipient’s phone. Upon receipt, the device reassembles the message if it was split into multiple segments. The message appears in the recipient’s messaging app, usually with a “delivered” confirmation if the network supports delivery receipts.

At this stage, the message is considered delivered. SMS does not provide read receipts, so the sender cannot know if the recipient has opened the message. This is a fundamental difference compared to internet-based messaging apps.

Step 5: Logging and Billing

Behind the scenes, the carrier logs every SMS transaction for billing and monitoring purposes. Each message, including its size and destination, is recorded. Even though the user experiences an almost instantaneous process, the message has traveled through multiple layers of network equipment, storage servers, and transmission protocols to reach the recipient. You can even text using an existing business phone number, landline, or VoIP if you are in the US or Canada by using services like Texty Pro.