29.1633GPPInterworking between the IP Multimedia (IM) Core Network (CN) subsystem and Circuit Switched (CS) networksTS
This annex provides optional interworking procedures to support facsimile transported according to ITU-T Recommendation T.38  transported according to IETF RFC 3362  in the "UDPTL" transport format. Related Mn Signalling Procedures are also described.
To enhance interoperability, recommendations for an MGCF T.38 configuration are also provided.
NOTE: Alternatively, facsimile can also be transported as inband voice band data over IP.