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Figure 12-4

System Series Control Point

NOTE

All SNA communication is between NAUs.

Subareas

When SNA was developed, the architecture of SNA subareas was introduced. Later, another
concept called APPN was developed to improve communications in the SNA network. APPN
is discussed in the next chapter. This section discusses the concepts of SNA subareas, along
with some of the differences with APPN.

A subarea consists of a subarea node and all the peripheral nodes attached to it, similar to a
domain concept. Subarea nodes are mainframes and front-end processors. An example of a
peripheral node is a cluster controller.

Subarea SNA resources are controlled from a central location, usually the mainframe. A
mainframe connected to a FEP would not be considered a subarea because the FEP is not a
peripheral node; it is a subarea node. A subarea consists of one subarea node (think mainframe)
and all the resources it controls. A subarea node is a node (think mainframe, front-end
processors) that can communicate with other subarea nodes (think front-end processors) and its
own peripheral nodes (think cluster controllers, PCs, printers, and so on). Figure 12-5 shows
several subareas, each controlled by a subarea node.

Mainframe

IBM 3174

SNA Domain CCDP

SSCP

SSCP defines and controls the SNA domain

SSCP activates and deactivates links

SSCP contacts and disconnects link stations

LU-LU session

87200333.book Page 439 Wednesday, August 22, 2001 2:53 PM