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30 Chapter 1
SNA Terms and Concepts
Basic SNA Concepts
Node Types in a Peer Network
Peer networks do not classify nodes hierarchically, as is done in a
subarea network. Exchanges with other nodes are not controlled by a
host or other centralized processor. Instead, any node can establish
communication with any other node.
A peer network is composed of type 2.1 nodes. The nodes in a peer
network can serve the following roles:
• APPN network nodes (NNs) identify the locations of network
resources, determine routes for sessions between these resources,
route sessions, and serve end nodes (EN) and low-entry networking
(LEN) nodes directly attached to the network node. The domain of an
APPN network node consists of itself and any end nodes for which it
provides network services.
• APPN end nodes can access remote resources without requiring that
those resources be configured on the end node. An end node can
communicate with adjacent nodes on its own, but requires the
services of a network node server to access nonadjacent nodes. The
domain of an APPN end node includes only itself.
• Low-entry networking nodes (LEN nodes) are type 2.1 nodes that do
not support APPN functions. They can communicate with adjacent
nodes in an APPN network, but do not participate in the APPN
network. In a LEN node, all potential sessions with remote LUs must
be predefined, either specifically or through a single default entry
indicating that all remote LUs reside in an adjacent network node
that can be accessed using a certain link. The domain of a LEN node
includes only itself.
For more information about peer-oriented node types, see “APPN Node
Types”.
Connectivity
For two nodes to communicate, each node must have a combination of
hardware and software that supports data flow between the nodes. The
hardware component consists of an adapter at each node and the
transmission medium that connects the two adapters. The software
component provides control of the hardware and the data exchanged over
it.