HP-UX SNAplus2 R7 Administration Guide

SNA Terms and Concepts

Basic APPN Concepts

• 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

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

An example of a LEN node directory is 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.

Figure 1–5 LEN Node Directory

Node LEN1

Node LEN1 Directory:

LUA - Node NNA

LU1 - Node NNA

LU3 - Node NNA

Node EN2

Node EN1

Node NNA

LU3

LUA

LU2

LU1

To establish a session with an LU on a node that is not directly attached, Node LEN1 sends an LU-LU session ac-

tivation (BIND) request to its network node server (Node NNA). The server automatically locates the destination

LU and forwards the BIND.

Note

In this example, Node LEN1 can establish a session with LU1 on Node EN1 through its

network node server, NNA. However, LU2 on Node EN1 is not deﬁned in the directory for

Node LEN1, so Node LEN1 cannot establish sessions with that LU.

End Node Directories

When an LU is not represented in an end node directory, the end node initiates a LOCATE search to ﬁnd the desired

LU. To activate the search for a remote LU, the end node invokes the services of its network node server. An

example of an end node directory is shown in Figure 1–6, End Node Directory.