HP-UX SNAplus2 R7 Administration Guide

SNA Terms and Concepts
Basic SNA Concepts
For example, LU type 1 can support an application program running under Information Management System/
Virtual Storage (IMS/VS) and communicating with an IBM 8100 Information System. This enables an
operator to correct a database that the application program maintains.
Applications that use LU 1 are often described as remote job entry (RJE) applications.
LU 0 (for LUA)
LU 0, an early LU definition, supports primitive program-to-program communication. Certain host database
systems, such as IMS/VS (Information Management System/Virtual Storage) and some point-of-sale systems
for the retail and banking industries (such as the IBM 4680 Store System Operating System) use LU 0.
Current releases of these products also support LU 6.2 communication, which is the preferred protocol for
new applications.
Note
For information about the data streams used by SNA logical units, refer to Systems Network
Architecture Technical Reference.
Control Points
A control point (CP) is an NAU that manages network resources within its domain, controlling resource activation,
deactivation, and status monitoring. The CP manages both physical resources such as links, and logical information
such as network addresses.
SNA defines the following types of network control points:
System services control point
On a type 5 node, the CP is called a system services control point (SSCP). It manages and controls the
network resources in a subarea network. For example, an SSCP can use a directory of network resources
to locate a specific LU under its control, and can establish communication between two LUs in its domain.
An SSCP can also cooperate with other SSCPs to establish connectivity between LUs in different subarea
domains.
The SSCP also provides an interface to network operators at the host system, who can inspect and control
resources in the network.
Physical unit control point
On type 4 nodes and type 2.0 nodes in a subarea network, the control point is called a physical unit control
point (PUCP).
Control point
On type 2.1 nodes, the control point provides both PU and LU functions, such as activating local link stations,
interacting with a local operator, and managing local resources. It can also provide network services, such as
partner LU location and route selection for local LUs.
In a subarea network, the CP on a SNAplus2 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 Section 1.3.2, APPN
Control Point.
1.2.7 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.
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