HP-UX SNAplus2 R7 Administration Guide

SNA Terms and Concepts
Basic SNA Concepts
1 SNA Terms and Concepts
This chapter defines Systems Network Architecture (SNA) terms and concepts that are important to understanding
and using SNAplus2. For information about SNAplus2, its capabilities, and how it implements the different SNA
concepts described, see Chapter 2,
Introduction to SNAplus2. If you are already familiar with SNA and SNAplus2,
you can begin with Chapter 3, Administering SNAplus2.
This chapter is divided into the following parts:
• Section 1.1, Systems Network Architecture provides a definition of SNA.
• Section 1.2, Basic SNA Concepts explains terms and concepts that apply to any SNA network.
• Section 1.3, Basic APPN Concepts explains terms and concepts that apply only to SNA networks that support
Advanced Peer-to-Peer Networking (APPN).
• Section 1.4, Accessing Subarea Networks from APPN Networks introduces terms and concepts that apply to
networks that combine SNA and APPN.
Note
This chapter is not intended as a complete reference to SNA concepts. Detailed information
about SNA can be found in the SNA publications listed in Related Publications.
1.1 Systems Network Architecture
Systems Network Architecture (SNA) is an IBM data communication architecture that specifies common conventions
for communicating among a wide variety of hardware and software data communication products. This architecture
consists of two kinds of definitions: formats that define the layout of messages exchanged by network components,
and protocols that define the actions that network components take in response to messages.
An SNA network is a collection of computers that are linked together and communicate using SNA.
Originally, SNA was designed to enable communications with a host computer. Each network or subnetwork was
controlled by the host; other computers communicated directly with the host, but not with each other. This older,
host-controlled style of network is often referred to as subarea SNA. SNA has since been extended to support direct
peer-to-peer communications between computers in the network, without requiring a host. This newer, peer-level
networking is APPN.
Many SNA networks have elements of both subarea and peer-to-peer networking. As networks migrate from
subarea SNA to APPN, an APPN-capable host may act to control older systems while also acting as a peer to
newer systems. Similarly, a single computer may access both peer computers (in an APPN network) and an older
host; its communications with the host are controlled by the host, but its communications with other computers are
peer-to-peer and do not involve the host.
1.2 Basic SNA Concepts
SNA defines the standards, protocols, and functions used by devices—from mainframes to terminals—to enable
them to communicate with each other in SNA networks.
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