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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.
• An APPN end node maintains a directory that includes its own LUs.
It can also be configured to store directory entries for partner LUs in
adjacent nodes. This enables local LUs to establish peer-to-peer
sessions with those LUs without using APPN functions.
If a resource is not locally defined to an end node or currently cannot
be reached by the end node, the end node sends a request to its
network node server asking it to search the APPN network for the
resource.
• An APPN network node maintains a directory that includes its own
LUs and the end node and LEN node LUs in its domain. An end node
can dynamically register its LUs with its network node server. (LEN
nodes cannot register LUs with a network node server, so LEN node
LUs must be configured on their network node server.) A network
node directory can also contain cached entries for LUs that are not in
the network node's domain, but whose location has been determined
through a previous search.
Network nodes provide directory services to other nodes in two ways:
• Searching for remote resources in response to session requests
from end nodes or LEN nodes
• Responding positively to directory search requests from other
network nodes when a named resource is found in the local
directory
LEN Node Directories.
shown in Figure 1-5, "LEN Node Directory." Since LEN nodes do not
support CP-CP sessions, the directory for Node LEN1 must contain all
the LUs with which it communicates. The directory for Node LEN1
identifies its network node server (NNA) as the location for any LUs that
are not on an adjacent peer end node. Since Node LEN1 can access the
LUs only through Node NNA, it defines the CP on the network node as
the "owning CP" of all the LUs, including LUs located on the end nodes.
Chapter 1
An example of a LEN node directory is
SNA Terms and Concepts
Basic APPN Concepts
49
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