Related specifications
RFC 3323, A Privacy Mechanism for the Session Initiation Protocol (SIP), available at http://www.ietf.org/
RFC 3325, Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks, available at http://www.ietf.org/
Implementation notes
In the MO direction, support is provided for:
Privacy header. Note that the header value is id when CLIR is on. (Section 9.3, RFC 3325 and Section 4.2, RFC 3323.)
From header, when CLIR is on, is set as Anonymous <sip:[email protected]>. (Section 4.1.1.3, RFC 3323.)
In the MT direction, the From header is checked to determine if an anonymous call is being made.