HP UX SNAplus2 manual Basic SNA Concepts

SNA Terms and Concepts

Basic SNA Concepts

A type 4 or 5 subarea node to which a peripheral node is attached acts as a boundary node. It performs a boundary function by translating between the network addresses used by a subarea node and the local addresses used by a peripheral node.

A simple subarea network includes the following components:

Host

A host is a mainframe computer compatible with the original IBM System/370. A host is a type 5 node.

Communication controller

A communication controller, also known as a front-end processor (FEP), is a separate processor attached to the host. It manages the host's communications with other computers.

Communications link

A communications link connects the host site with an end-user site. The users are usually on a separate site from the host, so the two sites need to be connected by a communications link.

Terminal controller

At the remote end of the communications link is a terminal controller, also known as a cluster controller. It is responsible for controlling the use of the link, and routes data to the terminals. The most well-known IBM terminal controllers are the 3174 and 3274.

Terminals

Users run host applications or submit work to the host from terminals. The best-known IBM terminal is the 3270. A terminal can be connected through a terminal controller or directly connected to a communication controller.

Printers

Printers such as the IBM 3287 can also be attached to the terminal controller. They can receive output from the host.

As shown in Figure 1-1, “SNA Subarea Network,” a diagram of a subarea network looks like an inverted tree.

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