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Chapter 2 93
Introduction to SNAplus2
SNAplus2 Resources
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 define 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, FDDI or
Ethernet 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.