SIMPLE

SIP for Instant Messaging and Presence Leveraging Extensions (SIMPLE) is based off of SIP and is a developing open standard protocol for instant messaging. Despite its name, SIMPLE is defined by about 30 documents or more than 1000 pages (7 times more than HTTP 1.1, 15 times more than SMTP and IRC). Some of it has been standardized by the IETF, other parts are still works in progress.