HP-UX SNAplus2 R7 Administration Guide

SNA Terms and Concepts
Basic APPN Concepts
• Two parallel CP-CP sessions are established between an APPN end node and the adjacent network node acting
as the server for the end node. These CP-CP sessions are used to exchange directory, topology, and management
services data.
• LEN nodes do not support CP-CP sessions.
The functions provided in CP-CP sessions vary based on the types of nodes involved, as follows:
• All CP-CP sessions conduct directory searches.
• CP-CP sessions between an end node and a network node provide the following functions:
• Registering resources.
• Routing management services data (such as alerts) between the end node and a focal point.
• Routing topology data from each end node to its network node servers. This information can be used by
the network node server to compute a route that does not flow through the network node server.
• CP-CP sessions between adjacent network nodes exchange topology information. As a result of this exchange,
each network node creates an internal network topology database.
When setting up a node, you must define the CP name. The CP is also an LU that can support user sessions, and
it can be the only LU defined in your node, if you so choose.
1.3.3 Locating Resources
To support communication between TPs, SNAplus2 first establishes a session between the logical units that control
those TPs. APPN enables the CP on a node to locate LUs throughout the APPN network without requiring that
the node have any configuration information for the remote LU. The APPN function that dynamically locates LUs
in the network is called directory services. Once a resource has been located, a route for the session is calculated
through the APPN network.
Resource Names
Each node has a unique name consisting of two parts: a network name and a control point name. Together they
constitute a fully qualified CP name. This name identifies each node to all other nodes in the network. Similarly,
each logical unit is identified by a fully qualified LU name, consisting of a network name and LU name.
Directory Services
Each APPN node maintains a directory of network resources. Directory services is the component of the node CP
that manages the local directory database and, in a network node, searches for network resources throughout an
APPN network.
When the node is initialized, it includes the following information:
• Node type (APPN network node, APPN end node, or LEN node)
• Network ID of node
• CP name of node
Each node directory maintains entries for resources (LUs and CPs), including each resource’s fully qualified name,
type, and registration status. The specific resources stored in each local directory depend on the node type:
• A LEN node maintains a directory that includes its own LUs. It must also be configured with directory entries
for all of its possible partner LUs. LUs in the APPN network with which the LEN node may want to establish
sessions must be defined to the LEN node as if they reside on the LEN node’s network node server. The LEN
node establishes sessions with LUs on its network node server. The network node routes the session through
the APPN network to the proper node in the network.
A LEN node can also use wildcards in a directory entry to specify multiple partner LUs that can be accessed
over a specific link.
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