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Chapter 1 45
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.