HP -UX SNAplus2 Administration Manual page 29

SNA Terms and Concepts
Basic SNA Concepts
Figure 1-1 SNA 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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