Systems Network Architecture was a proprietary networking protocol developed by IBM in 1974 for mainframe connectivity. It overcame communication port issues and allowed trunk bundles to connect, making it popular in the financial industry. Although outdated, it is still used in some companies today.
Systems Network Architecture is a proprietary networking protocol owned and marketed by International Business Machines (IBM) from 1974 to 2002. This protocol contains a group of interconnected applications, protocols, and services that run on the IBM 3745/3746 communications controller. This controller is still common in thousands of different companies, especially financial companies like banks and brokerage firms. Although production of the IBM 3745/3746 communications controller has been discontinued, the system continues to receive updates from IBM, and a variety of third-party systems use the controller as their base hardware.
The point of the Systems Network Architecture protocol was the connection of mainframe computers with other mainframes and communication terminals. This process was mainly achieved through landline connections and telephone lines. When this technology hit the market in the mid-1970s, the industry with the greatest need for fast, reliable interconnectivity was banking. As a result, systems network architecture has become a common method for exchanging information between financial systems.
This technology was designed to overcome two major technological disadvantages of the time. This first problem was the communication system itself. Terminals and mainframes of the time used wired communication ports to communicate with each other. These ports were faulty in their own right, but when ports of different makes or models tried to communicate, the failure rate often made connectivity impossible. The systems’ network architecture was a technological overlap that forced different ports to operate the same way, reducing error rates.
The other big drawback was being built directly into IBM systems. At the time, the telephone network was so poor that transmissions were extremely slow. To overcome this technological limitation, large computers used trunk bundles to connect. Each of these bundles had hundreds of communication lines. Even though the connection was slow, so much information flowed across the different lines that it allowed for reasonable transmission speeds.
IBM systems had a hard-coded limit of 256 peripheral connections per processor. While this was fine for most systems as they only had a handful of printers and keyboards attached, each line connection counted as its own peripheral. This severely limited the size of trunk groups available to the computer. Systems Network Architecture allowed the system to read a group of lines as a single device, increasing the number of available connections.
As computing has changed, the network architecture of systems has changed with it, but not fast enough. Modern protocols and processing methods have made some aspects of systems network architecture cumbersome or obsolete. As a result, when the contract to manufacture the IBM 3745/3746 communications controller expired in 2002, it was not renewed. A third party system continued to produce the controller and upgrade kits until 2009.
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