An Extension to the Session Initiation Protocol for Request History Information
This draft defines a standard mechanism for capturing the history information associated with a SIP request. This capability enables many enhanced services by providing the information as to how and why a call arrives at a specific application or user. This draft defines a new optional SIP header, History-Info, for capturing the history information in requests. A new option tag, HistInfo, to be included in the Supported header is defined to allow UAs to indicate whether the HistInfo should be returned in responses to a request which has captured the history information.