http://www.rfc-editor.org/rfc/rfc7131.txt
RFC 7131: Session Initiation Protocol (SIP) History-Info Header Call Flow Examples, M. Barnes, F. Audet, S. Schubert, H. van Elburg, C. Holmberg2014-03-01T23:00:00-00:00This document describes use cases and documents call flows that require the History-Info header field to capture the Request-URIs as a Session Initiation Protocol (SIP) Request is retargeted. The use cases are described along with the corresponding call flow diagrams and messaging details.