Instant messaging (IM) has long been one of the most common and popular methods of communicating over IP networks. Whereas VoIP uses voice communication and videoconferencing uses live images and sound, IM simply uses text messages to allow participants to converse. These text messages are sent in real-time between the users who use the same IM application, and allows an individual to essentially create a private chat room with another individual where they can send text messages to one another. Many applications will even provide the ability to add additional participants to the chat, creating a text-based conference room of multiple users.

To manage the messages and identify whether specific users are online, an extension of SIP for instant messaging has been developed. SIMPLE is an acronym that stands for the Session Initiation Protocol for Instant Messaging and Presence Leveraging Extensions. Although the name is ironically less than simple to remember, it is being developed as an open standard for how individuals can determine the status of a person (i.e., whether they are online, busy, etc.), and for managing the messages that go back and forth between the participants in a chat.