Encapsulating SNA With ANYNET In an effort to provide better support for TCP/IP on SNA hosts, IBM offers ANYNET. ANYNET is basically SNA traffic encapsulated inside TCP/IP. The benefit of using ANYNET is that most of the software developed for SNA clients and hosts can be retained, while customers are provided with a viable method to use TCP/IP as the transport. Many customers demand higher levels of functionality as found in traditional SNA applications instead of relying on standard TCP/IP client tools like telnet and FTP. On the client side, application data is taken from an SNA-aware application, such as a terminal emulator, encapsulated in the TCP/IP protocol and sent to the host. On the host side, the packets are translated back into SNA and passed on to the host application. Obviously, the reverse happens to packets destined for a client. In theory, it is very much like a gateway but instead of a hardware/software component sitti ng in the middle providing TCP/IP-SNA translation, the translation occurs on the host itself. For terminal traffic alone-even in high workload situations-ANYNET usually performs well, with response times as fast as a gateway. But performance is directly dependent on how many packets must be translated. With terminal traffic, on average, most transactions occur with one to two packets being sent to the host, and one to three packets returned, depending on packet size. Total data exchanged per transaction could be from 2 KB to 6 KB. Throw in client/server applications, where data traffic can increase to 10 KB, 25 KB and beyond, and things get a little muddy. Even worse, consider file transfer, where thousands of packets must be translated by the host and client. Our test proved to be a nightmare for ANYNET, since more than 1 GB of data had to be translated by the host-which was also perfo rming normal communication functions and running the host's transfer components. Most of the cost/performance equations we have examined seem to favor the gateway solutions, but with recent advances in host performance and software, the gap seems to be closing. Before getting into a gateway solution, examine the numbers for yourself. Balance the cost of the additional CPU power required for ANYNET against the cost of the gateway software.

How We Tested SNA Gateways Return to A tale of Two Gateways: Bridging the Old and New by Jon Crisler and Thanh Nguyen ISDN PC Cards Adapters: Tiny Bundles of Remote Connectivity Pack a Punc h by Jeffery L. Carrell Updated June 27, 1997