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Chapter 10: TN3270 Enhanced > 10.2: TN3270 Enhanced (TN3270E) - Pg. 260

10.2 TN3270 Enhanced (TN3270E) Today, a single instance of the TN3270E server can support up to 128 000 emulated 3270 display terminals. Display terminals are emulated in software called TN3270E clients , which can run on a standard personal computer or workstation. In the world of genuine 3270 display terminals, 128,000 end users would require an enormous amount of dedicated, limited function keyboard and display devices, not to mention 2000 dedicated 3174 control units! As network usage exploded, the SNA 3270 method of communicating with a mainframe became untenable. The solution came in the form of the Internet Protocol (IP). 10.2.1 Telnet protocol and SNA meet The original basic telnet protocol was defined in RFC 854. This RFC effectively defined all that was needed to support the 3270 data stream, since the 3270 data stream is just part of the telnet data payload. In other words, the 3270 portion was implemented outside of (above) the telnet protocol. Specific options could be negotiated (beyond basic telnet) using the telnet option standard of RFC 855. Option negotiation in turn allowed for device type negotiations (later formally defined in RFC 1091) to be completed as part of the telnet session setup.