An updated internet-draft is available from the IETF. This draft is a work item of the Internet Fax Working Group of the IETF.
Abstract: «To allow connectivity between the general switched telephone network facsimile service (GSTN fax) and the e-mail based Internet Fax service (i-fax) an “Internet FAX Gateway” is required. This document provides recommendations for the functionality of Internet FAX Gateways. In this context, an “offramp gateway” provides facsimile data transmission from i-fax to GSTN fax; viceversa an “onramp gateway” provides data transmission form GSTN fax to i-fax. The recommendations in this document apply to the integrated service including Internet Fax terminals, computers with i-fax software on the Internet, and GSTN Fax terminals on the GSTN.»