Abstract

Testing Unix-to-SNA Gateways

This May 1994 Data Communications lab test, conducted by Kevin Tolly of The Tolly Group and David Newman of Data Communications, evaluated Unix-to-SNA gateway products designed to connect Unix workstations and servers to IBM SNA host environments. The article examined whether Unix systems could be integrated successfully into corporate SNA networks, and whether these gateways could provide reliable 3270 terminal emulation, file transfer, APPC support, management, and host connectivity without forcing organizations to abandon existing mainframe infrastructure.

The lab tested products from Brixton Systems, Hewlett-Packard, IBM, and Unisys. The test focused on gateway architecture as much as feature count. Products were compared across full-stack and split-stack designs, upstream host connectivity, downstream client support, 3270 emulation, LU support, file transfer, APPC programming, configuration, management, and price. The lab also evaluated practical deployment issues, including how easily managers could configure the gateway, control sessions, collect statistics, trace problems, and support multiple Unix and PC client operating systems.

The results showed that all four vendors could provide workable Unix-to-SNA connectivity, but with very different architectural trade-offs. Full-stack gateways placed the complete SNA protocol stack on the gateway and made Unix clients appear more like downstream SNA users. Split-stack approaches relied on TCP/IP between clients and the gateway, simplifying some Unix-side deployment issues but shifting more intelligence to client software. The article emphasized that gateway architecture mattered more than any single checklist feature because it affected scalability, management, client support, and long-term interoperability.

IBM received a Data Communications “Tester’s Choice” designation for its SNA Server/6000 and SNA Gateway/6000 products. The lab found that IBM offered the most complete SNA implementation and strong configuration control, making Unix and TCP/IP clients behave more like native SNA users. IBM’s approach was powerful, though it could require more components and more administrative planning than simpler alternatives.

Unisys also received a Data Communications “Tester’s Choice” designation for its Enhanced SNA Gateway. The article praised Unisys for ease of setup, strong management routines, and fast file-transfer performance. Unisys took a fill-in-the-blanks approach to configuration that made the product comparatively easy to bring online, and its gateway delivered the fastest IND$FILE transfer results in the lab.

Brixton’s BrxPU2.1 SNA Server and Brx3270 emulator showed strong Unix orientation and broad client support, but the article noted that configuration and management were more complex. Hewlett-Packard’s SNA Plus Link and SNA Plus 3270 products offered a split-stack design and aggressive pricing, but the lab found limitations in client-side functionality and management integration.

Overall, the article concluded that Unix-to-SNA gateways had become practical tools for enterprises that needed to blend Unix, TCP/IP, and IBM SNA environments. However, buyers needed to look beyond terminal emulation and compare gateway architecture, host connectivity, LU support, APPC capabilities, management tools, and client software requirements. The strongest products made SNA access from Unix systems manageable, but product choice depended heavily on each organization’s host environment, Unix platforms, and administrative model.

Solutions Tested

Brixton Systems — BrxPU2.1 SNA Server
Brixton Systems — Brx3270

Hewlett-Packard — SNA Plus Link
Hewlett-Packard — SNA Plus 3270

IBM — SNA Server/6000
IBM — SNA Gateway/6000
IBM — AIX 3270 Host Connection Program (Hcon)

Unisys — Enhanced SNA Gateway (e/SNA)
Unisys — Enhanced SNA 3270

Note: The last several pages of this article were missing from the scanned original magazine.