Using T.38 and SIP for real-time fax transmission over IP networks

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. We study the use of T.38 facsimile in conjunction with session initiation protocol (SIP) for transmission of fax traffic over IP networks. Since the interactions of these protocols are not completely standardized, we investigate and propose some practices for this transmission process. Through network simulations of both signaling and data traffic, we determine that real-time fax transmission using SIP is achievable and that it is important to utilize the SIP contact-header for reducing the load on SIP proxy servers and links associated with them.