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 CS/AIX 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.