Terminal Access to IBM Mainframes

Users who need access to IBM SNA–based mainframe computers generally use the 3270 data stream, a protocol that defines how components in hierarchical SNA networks can gain access to IBM mainframe computers. The 3270 data stream uses LUs to support 3270 Display Devices such terminals and terminal emulators (LU 2), 3270 Printer Devices (LU 1 or LU 3), and applications (LUA). A 3270 LU is known as a dependent LU because it requires a mainframe to function.

Clients can use several variations of 3270 type display terminals and terminal emulators (LU 2) to gain access to SNA resources:

• 3270 terminals and terminal emulators.
• 3278 terminals and terminal emulators (models 2, 3, 4, and 5).
• Telnet-based (TN3270) terminal emulation types, including TN3270E (extended TN3270) and Web browser–based terminal emulators.

Telnet terminal emulators allow TCP/IP-based computers to gain access to host systems that support TCP/IP access or through gateways that convert TCP/IP communications to native SNA.

Note

SNA Server supports both 3270 and TN3270 access methods.

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