http://www.rfc-editor.org/rfc/rfc6914.txt
RFC 6914: SIMPLE Made Simple: An Overview of the IETF Specifications for Instant Messaging and Presence Using the Session Initiation Protocol (SIP), J. Rosenberg2013-04-01T23:00:00-00:00The IETF has produced many specifications related to Presence and Instant Messaging with the Session Initiation Protocol (SIP). Collectively, these specifications are known as SIP for Instant Messaging and Presence Leveraging Extensions (SIMPLE). This document serves as a guide to the SIMPLE suite of specifications. It categorizes the specifications, explains what each is for, and how they relate to each other.