Mainframe Connection Summary

The hierarchical SNA network model provides access to a centralized processing resource from elements on the network. This model is most frequently associated with mainframe environments in which centralized applications are accessed from remote terminals across a network.

Devices in a hierarchical SNA network, such as terminals or cluster controllers, are called physical units (PUs). Each class of device is designated by a number. For example, the mainframe itself is known as a PU 5 device.

Figure 4.6 Connections in a hierarchical network.

SNA Server can directly connect to the mainframe, if a high-performance connection is required. These physical connection methods are available:

• Open Systems Adapter, supporting token ring, Ethernet, and FDDI connections

• Bus & Tag channel connection

• ESCON channel connection

Connections to a front-end processor (FEP), which is a PU 4 device, are also supported. These types of connections may be easier to implement depending on your existing infrastructure and the physical proximity of the SNA Server to the mainframe. For this type of connection, one of these methods can be used:

• Token ring

• Ethernet

• FDDI

• SDLC

• X.25

In a hierarchical SNA network, SNA Server emulates a cluster controller and supports all standard protocols:

• LU 2, for 3270 terminal sessions

• LU 1 or 3, for SCS or 3270 printer sessions

• LU 6.2, for APPC and CPI-C applications

• LU 0, 1, 2, or 3, for LUA RUI/RI general-purpose, customized applications

Any combination of these protocols may be used over a given physical connection.