SNA Terms and Concepts

Basic SNA Concepts

In a subarea network, the CP on an SNA node acts as a type 2.0 PU. It communicates with an SSCP on a host and does not communicate with other CPs in the subarea network.

When participating in an APPN network, the CP exchanges network control information with the CPs in adjacent nodes. The CP can also function as an independent LU of type 6.2. The CP acts as the default LU for TPs on the local node. For more information about the APPN control point, see “APPN Control Point”.

Sessions

NAUs communicate with NAUs in other nodes over temporary logical communication channels called sessions. Before two TPs can communicate, their LUs must establish a session. The LU that manages the session on the local node is the local LU; the LU that manages the session on the remote node is the partner LU.

Session Types

SNAplus2 is primarily concerned with the following types of sessions:

LU-LU sessions

In order for two TPs to communicate, the LUs that support the TPs must first establish an LU-LU session. In general, a session is established when a TP in one SNA node tries to communicate with a TP in another node and no existing session between the LUs on the two nodes is available.

SSCP-LU sessions

A dependent LU (see “Dependent and Independent LUs”) must have an active SSCP-LU session with an SSCP on a type 5 node before it can have a session with an LU in the subarea network. Once an SSCP-LU session is active, a dependent LU can solicit an LU-LU session.

SSCP-PU sessions

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Chapter 1