Is your text message a SMS message?

SMS messages are often regarded as being synonymous with text messages, but actually there are several different types of text messages.

OTT (over the top) messages are sent via the internet - no carrier is necessary - a message can be sent on the web, or using an app. WhatsApp and Facebook Messenger are widely used OTT messaging apps. SMS (short message service) systems use a cellular network connection It's not necessary to have a smartphone to send a SMS message. Mobile phones use the SMPP (short message peer-to-peer protocol) whenever a SMS message is sent. OTT messaging apps use various internet protocols such as RTSP (Real Time Streaming Protocol). WhatsApp uses the Extensible Messaging and Presence Protocol (XMPP)

A SMS text message system will not require access to other apps, or the mic and camera of a smartphone as OTT apps often do. SMS messaging is more likely to be subject to government regulations restricting SPAM.

A SMS text message is limited to 160 characters. Many mobile phones use MMS (multimedia messaging service) to send text messages which allows for a larger number of characters, and also photos, videos, and audio which could not be sent in a SMS message. MMS is based on SMS technology. Often MMS messages will be limited to 300 KB - 600 KB. Such limitations will not apply to OTT messages.

The IMessage app on an Apple iPhone sends texts via Apple's servers. They differ from standard SMS messages in that they use end-to-end encryption. An iMessage text can be sent via a cellular network if internet access is not available.