APPC Subsystem on MPE/XL Node Manager's Guide (30294-90007)

Chapter 1 21
Introduction
The APPC Subsystem
The APPC Subsystem
The APPC subsystem is a component of several of Hewlett-Packard's
LU 6.2 products; multiple LU 6.2 products on the same node use one
APPC subsystem. The APPC subsystem implements the base set of
basic conversation verbs and certain option sets. These verbs are
implemented as intrinsics that are accessed by the transaction
programs associated with Hewlett-Packard’s LU 6.2 products.
Structure of the HP 3000 Node
The APPC subsystem implements the Data Flow Control and
Presentation Services layers of the SNA architecture. SNA/SDLC
Link/XL must be installed on the same processor with the APPC
subsystem. SNA/SDLC Link/XL provides the Path Control and
Transmission Control layers of SNA. Figure 1-2 shows the APPC
subsystem and the SNA link product as they relate to the SNA
architecture.
Figure 1-2 The APPC Subsystem in the SNA Architecture
NOTE SNA/X.25 Link/XL can be used in place of SNA/SDLC Link/XL, but
SNA/X.25 Link/XL emulates a Type 2.0 node, not a Type 2.1 node.
Therefore, if you run the APPC subsystem on top of SNA/X.25 Link/XL,
all your HP 3000 LUs must be dependent LUs, and you cannot
communicate peer-to-peer with a Type 2.1 node like an AS/400.