http://www.rfc-editor.org/rfc/rfc8048.txt
RFC 8048: Interworking between the Session Initiation Protocol (SIP) and the Extensible Messaging and Presence Protocol (XMPP): Presence, P. Saint-Andre2016-12-01T23:00:00-00:00This document defines a bidirectional protocol mapping for the exchange of presence information between the Session Initiation Protocol (SIP) and the Extensible Messaging and Presence Protocol (XMPP). This document obsoletes RFC 7248.