SNA Terms and Concepts

Basic SNA Concepts

Figure 1-1SNA Subarea Network

The root of the tree (at the top of the diagram) is the computer controlling the network. The branches are the communications links from the host to the other computers in the network (terminal controllers); the leaves (at the bottom of the diagram) are the terminals or printers attached to these computers, which are accessed by users.

The traditional subarea SNA set-up described here enables the users to use the resources of a single host system. The terminals provide only simple data entry and display functions to and from the terminal controller; the terminal controller is responsible for handling SNA communications between the terminals and the host.

The terminal controller and its terminals can be replaced by an SNA node using a product such as SNAplus2. From the host's point of view, the node appears as a terminal controller. However, it provides the users with additional functions, such as the ability to access more than one host system and facilities for customizing screen displays. In addition, SNAplus2 runs on HP-UX computers that can also be used for other tasks not related to SNA (unlike the terminal controller, which is used solely for communications with the host).

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