Early terminals and host systems utilized a range of proprietary technologies that governed everything from display, input, keyboard layout, communications protocols and more - in almost all cases these were incompatible with competitor's offerings. Historically, IBM 3270 and 5250 series terminals utilized IBM's proprietary Systems Network Architecture(SNA) protocol to define how they communicated with their respective host systems. SNA was a predecessor of the now ubiquitous TCP/IP suite of networking protocols that powers modern networks, including the internet. The development of TN3270 was a crucial step in allowing a 3270 terminal emulator to communicate over a TCP/IP network instead of an SNA network. TN stands for telent, an application protocol which permits communications via TCP.