HP-UX SNAplus2 R7 Administration Guide

SNA Terms and Concepts
Basic SNA Concepts
SNA functions are divided into a hierarchical structure of separate layers, each performing a specific set of functions.
This division of network functions into layers enables network devices to share information and processing resources
without having detailed information about each device on the network. A user at a workstation can communicate
with another user without knowing anything about the physical devices on the network or the connections between
those devices.
1.2.1 Network Types
SNA supports the following types of networks:
• A subarea network is a hierarchically organized network consisting of subarea nodes and peripheral nodes.
Subarea nodes, such as hosts and communication controllers, handle general network routing. Peripheral nodes,
such as terminals, attach to the network without awareness of general network routing.
• A peer network is a cooperatively organized network consisting of peer nodes that all participate in general
network routing.
• A mixed network is a network that supports both host-controlled communications and peer communications.
Note
HP-UX systems running SNAplus2 can act as a peripheral node in a subarea network, as
a peer node in a peer network, or both at the same time.
1.2.2 SNA Nodes
In SNA networks, a node is a HP-UX system or other device—with associated software components—that
implements SNA protocols and has at least one communication path to another node in the network. Each node
manages its end of the network communication paths, and uses SNA protocols to communicate with the node at
the other end of each path.
Because subarea networks and peer networks define the relationships among nodes differently, they also use different
terms for node types (to describe the roles that nodes play in the network).
Node Types in a Subarea Network
SNA subarea networks support the following node types:
• Subarea nodes control communication and network resources for all attached nodes. SNA classifies subarea
nodes according to their capabilities and the amount of control they have over other nodes:
• Type 5 nodes provide SNA functions that control network resources, support transaction programs, support
network operators, and provide end-user services. Because these functions are often provided by host
processors, type 5 nodes are also known as host nodes. The devices and resources controlled by a type 5
subarea node constitute the domain of that node.
• Type 4 nodes provide SNA functions that route and control the flow of data in a part of the network.
Because these functions are often provided by communication controllers, type 4 nodes are also known as
communication controller nodes.
• Peripheral nodes serve subordinate roles in subarea networks. For example, a peripheral node can support 3270
emulation or dependent LU 6.2 communication. Peripheral nodes are devices such as distributed processors,
cluster controllers, or workstations; they are also classified into type 2.0 and type 2.1 nodes:
• Type 2.0 nodes are always controlled by a type 4 or 5 node. They cannot establish communication with
other nodes without the participation of a type 4 or 5 node. Type 2.0 nodes are referred to as dependent
nodes.
• Type 2.1 nodes can act as dependent nodes, but they can also communicate directly with other type 2.1
nodes.
16