IBM's Systems Network Architecture (SNA) is a protocol stack that IBM developed to address networking deficiencies that were prevalent at the time of its creation in 1974. Several large hardware and software vendors provide SNA gateways that connect LAN-based PCs with IBM host systems running SNA (Systems Network Architecture) protocols, including IBM, Microsoft and Hewlett Packard.

In the 1990's, fueled by a Gartner Group report stating that “users with SNA as their primary protocol will spend a total of 20% more than IP users on training staff, hardware and software purchases, and administration”, organizations began to migrate to Internet Protocol based networks.

TN3270 emulation is a communications standard that allows a remote terminal such as a Windows workstation to communicate with an IBM or IBM-compatible mainframe over IP. Similarly, TN5250 emulation uses the telnet protocol to create a TCP/IP connection to a remote host, typically an IBM AS/400 or iSeries server.

Now available on the market are non-invasive integration server solutions that allow customers to replace costly, aging SNA solutions with programmatic access to host-based applications at the data stream layer over an IP network. The host applications will traditionally be using 3270 (IBM Mainframe or zSeries) or 5250 (IBM AS/400 or iSeries) protocols and using LU types 0, 1, 2 or 3. A class library can be used to simply expose the information contained in these protocols to the customer's application prior to the construction of the screen and print buffers. This should not be compared to “screen scraping” API's such as HLLAPI or Object API offered by most terminal emulation vendors.

Typical customer applications requiring this interface are found in the banking and financial worlds, especially where the migration from SNA to IP networks has not yet been fully achieved. With the current state of the economy, some of the largest banks in the United States are now using this technology to eliminate thousands of servers and realize considerable savings in the process.

Many organizations continue to use TN3270E or TN5250E host printing, whether from an IBM zSeries mainframe or iSeries AS/400 midrange server. Using this type of programmatic IP-based integration solution, a developer can take a standard IBM 3287 LU 1 or LU 3 mainframe host printer session and programmatically output the information to multiple formats, including PDF, HTML, fax or file. This requirement can be found in banks, hotels, car rental agencies, hospitals, universities and state and local governments that continue to use host applications and need to output statements, receipts, invoices, reservations, class schedules, tax information, etc. in multiple output formats.

Using the LUA-RUI interface, existing LUA-RUI applications can be migrated from older, expensive SNA hardware and software solutions. Using the LUA RUI interface permits more control in customer applications by providing methods to handle exception requests, minimize LAN traffic through program design and recover from session failures.