IETF RFC 6913
Indicating Fax over IP Capability in the Session Initiation Protocol (SIP)
|Publication Date:||1 March 2013|
This document defines and registers with IANA the new "fax" media feature tag for use with the Session Initiation Protocol (SIP). Currently, fax calls are indistinguishable from voice calls at call initiation. Consequently, fax calls can be routed to SIP user agents that are not fax capable. A "fax" media feature tag implemented in conjunction with caller preferences allows for more accurate fax call routing.