SNA Terms and Concepts

Basic APPN Concepts

One of the APPN network nodes (NNA) also participates in a subarea network, connecting to a host through a communication controller. This node functions as an APPN node when communicating with nodes in the APPN network, and as a peripheral node when communicating with nodes in the subarea network. Through this network node, LU type 6.2 LUs on other nodes in the APPN network can establish LU-LU sessions with LU type 6.2 LUs on the host.

APPN Network Nodes

An APPN network node is a type 2.1 node that provides distributed directory and routing services for all LUs in its domain. These LUs can be located on the network node itself, or on an APPN end node or LEN node for which the network node provides services. Because an APPN network node acts as the network entry point for end and LEN nodes in its domain, the network node is also referred to as the network node server for those nodes.

A network node provides the following services:

•LU-LU session services for its local LUs

•Directory searches and route selection for all LUs in its domain

•Intermediate session routing (see “Intermediate Routing”)

•Routing for management services (MS) data, such as alerts, between a served end node and an MS focal point

APPN End Nodes

An APPN end node is a type 2.1 node that serves as an end point in an APPN network. It maintains directory information only for local resources. An APPN end node can independently establish sessions between local LUs and LUs on adjacent nodes. For sessions with LUs on nodes not directly connected to the end node, an end node requests routing and directory information from its network node server using CP-CP sessions.

APPN end nodes can register their local LUs with their network node server. This capability means the network operator at the network node server does not have to predefine the names of all LUs on the attached end nodes to which the network node provides services.

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