https://app.knowbase.one/vault/rfc/docid/4202
RFC3841: Caller Preferences for the Session Initiation Protocol (SIP)
Network Working Group J. Rosenberg Request for Comments: 3841 dynamicsoft Category: Standards Track H. Schulzrinne Columbia University ...
https://app.knowbase.one/vault/rfc/docid/5016
RFC4596: Guidelines for Usage of the Session Initiation Protocol (SIP) Caller Preferences Extension
Network Working Group J. Rosenberg Request for Comments: 4596 P. Kyzivat Category: Informational Cisco Systems July 2006 ...