HP-UX SNAplus2 R7 Administration Guide

Introduction to SNAplus2
SNAplus2 Resources
• A peer computer, with SNAplus2 and the remote computer communicating as equal partners (the typical
arrangement in an APPN network)
• A downstream computer, which uses the SNAplus2 PU concentration feature or DLUR feature as a gateway to
access a host.
A link station is associated with a specific port. One or more link stations can be defined on the same port.
Connection Networks
Connection networks cannot be used by LEN nodes.
Nodes that are connected to the same token ring, Ethernet, FDDI, or IP network have a direct communications path
between all nodes, so that in theory any two nodes can communicate directly. Such a network is referred to as a
shared-access transport facility (SATF).
The local node can have an explicit link station defined for its communication path to another node on the SATF,
but enabling communications between every pair of nodes on the SATF requires a large number of link station
definitions, and results in a large volume of network topology information flowing on the network.
APPN enables you to set up this type of configuration without having to define each link station explicitly, by
defining a connection network (CN) that represents the SATF. For each node on the SATF, you de
fine one or more
ports used to access the connection network. Instead of defining a link station to each remote node, you specify
the name of a virtual routing node (VRN) as part of the port definition.
You can think of the VRN as an imaginary node that represents all the other nodes on the SATF; you can give it
any name you like, but all nodes on the SATF must use the same VRN name (and it must not match the name of
any of the real nodes on the SATF). The local node can establish communications with any other node that has
a port associated with the same CN, by accessing the VRN (which represents all the other nodes attached to the
SATF), instead of requiring an explicitly defined communications path between each pair of nodes.
When two nodes on the SATF need to communicate and both have a port defined with the same VRN name, APPN
can dynamically establish a direct connection between them; you do not need any additional configuration.
Because the connection is direct and does not need to go through any intermediate nodes, using a connection
network reduces traffic on the LAN and improves performance. You should use connection networks wherever
possible to take advantage of this.
You can define CNs for communications using token ring, Ethernet, FDDI, or IP DLCs.
To use this feature, you first define a DLC and port for each node that accesses the SATF, and indicate that the
port should be defined on the connection network. You do not need to define any link stations; SNAplus2 sets up
a dynamic link station to the CN (and hence to any port on it) when required.
Note
In the Motif administration program, CNs are not shown as a separate resource, but are
included as part of the configuration of SATF ports.
2.4.2 Session Resources
The following session resources are used by SNAplus2:
• Logical units (see Section 2.4.2, Session Resources)
• Modes and their associated classes of service (see Section 2.4.2, Session Resources)
• Directory information (see Section 2.4.2, Session Resources)
Logical Units
An LU is the node’s point of contact with a user program (3270 emulation program, RJE workstation, APPC TP,
CPI-C application, or LUA application). LUs are divided into two categories:
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