HP-UX SNAplus2 R7 Administration Guide

SNA Terms and Concepts
Basic APPN Concepts
• EN1 to NNA
• EN1 to EN2
• EN1 to EN3
• EN1 to EN4
• EN1 to EN5
Figure 1–10 Definitions Needed for Direct Links from Node EN1 to Every Node in an
APPN Network
End Node 1 (EN1)
Link Definitions Needed for Node 1 EN1:
EN1 to NNA
EN1 ro EN2
EN1 to EN3
EN1 to EN4
EN1 to EN5
End Node 5 (EN5)
End Node 4 (EN4)
End Node 3 (EN3)
End Node 2 (EN2)
Network Node A (NNA)
If all of the nodes in the network are to support direct links to every other node, a total of 30 link definitions are
needed on the six nodes in this example. In general, the number of link definitions can be calculated as n
(n−1),
where n is the number of nodes in the network. In a larger network, the number of link definitions quickly becomes
unwieldy. Increasing the number of link definitions between network nodes also increases the number of TDUs
flowing through the network, which can degrade network performance.
APPN connection networks provide a solution to this problem.
APPN Connection Networks
For APPN networks attached to a shared-access transport facility (SATF), an APPN connection network greatly
reduces the number of link definitions needed to support direct connectivity between nodes in the network. In a
connection network, an APPN end node needs to configure only a single link to an adjacent network node server
and a link to the connection network, instead of configuring every possible link to every node.
To use the connection network feature, an APPN network must meet the following conditions:
• The nodes in the APPN network must be linked using switched media such as token ring or Ethernet (see
Section 2.4.1, Connectivity Resources).
• All of the links in the APPN connection network must use the same media.
• The APPN network that contains the connection network must be fully connected. In a fully connected network,
each node has at least one link that supports CP-CP sessions to an adjacent node.
In a connection network, the SATF serves as a virtual routing node (VRN) that attaches directly to each node in the
connection network. The name of the connection network serves as the name of the control point for the VRN. The
VRN supports the direct routing of session data between any two nodes in the connection network, but it does not
establish CP-CP sessions with other nodes and it does not generate TDUs. Each node in the connection network
requires only a link to its network node server.
The link definitions needed when using a connection network are shown in Figure 1–11, Definitions Needed for
Direct Links Using a Virtual Node. By using a virtual node, the connection network supports direct links between
Node EN1 and every other node in the APPN network, yet it requires only two link definitions.
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