HP-UX SNAplus2 R7 General Information

SNA Networking
SNA and APPN
An APPN end node provides limited APPN function support.
Each end node includes a control point; but it establishes CP-CP sessions with just one adjacent network node,
which becomes its network node server. The end node can receive network information from its network
node server so that remote LUs do not need to be defined. It can also register its own LUs with the network
node server, so that they are visible to remote nodes without the need for them to be pre-configured at the
remote nodes.
With the help of its network node server, an end node can establish LU-LU sessions with any other node in
the APPN network. An end node can also communicate without the help of a network node server, but this
is possible only if the remote node is directly connected and if the remote node and its LUs are con
figured
manually.
Unlike network nodes, end nodes do not support intermediate sessions carrying traffic for other nodes, so
they are restricted to the edges of the network.
APPN network nodes
An APPN network node provides the peer-oriented networking services that are fundamental to APPN.
Network nodes form the backbone of an APPN network. They can dynamically locate and connect to each
other, exchanging topology and configuration information and supporting intermediate sessions that enable
LEN nodes and end nodes to communicate across the network.
Each network node includes a control point that can establish a CP-CP session with any other adjacent network
node, and with any adjacent end node for which the network node is the network node server.
1.2.1 Branch Extender
Network nodes in an APPN network need to maintain topology information (about the location of other nodes
in the network and the communications links between them), and to forward this information around the network
when the topology changes. As the network grows in size, the amount of stored information and topology-related
network traffic can become large and difficult to manage.
It is possible to avoid these problems by separating the network into subnetworks, so that each node only needs to
maintain topology information about the nodes in its own subnetwork. However, this results in increased network
traffic when trying to locate resources in other subnetworks.
The Branch Extender feature of APPN, illustrated in Figure 1–3,
Branch Extender, provides a solution to these
problems.
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