Abstract: “Facsimile (fax) transmission is very important to the world of business. In a world where a significant percentage of long distance Public Switched Telephone Network (PSTN) traffic is composed of fax, great savings in toll charges are possible by utilizing IP networks instead.”

Keywords: Fax over IP, T.38, T.30, Session Initiation Protocol, Session description protocol, Proxy Servers, User agent client, Redirect Server.