SMS

Born in the GSM standard at the very end of the 1980s, the Short Message Service refers to sending short text messages. It had to slip into the signalling channels already present on the network, a constraint that explains its founding cap of 160 characters.

No text message jumps directly from one mobile to another: it is handed to a server centre (SMS-C) that holds it then pushes it to the recipient as soon as they become reachable again. This store-then-forward logic ensures delivery even when the device is switched off, and along the way masks everything about the sender beyond their number.