SNA Terms and Concepts

Basic SNA Concepts

Node Types in a Peer Network

Peer networks do not classify nodes hierarchically, as is done in a subarea network. Exchanges with other nodes are not controlled by a host or other centralized processor. Instead, any node can establish communication with any other node.

A peer network is composed of type 2.1 nodes. The nodes in a peer network can serve the following roles:

•APPN network nodes (NNs) identify the locations of network resources, determine routes for sessions between these resources, route sessions, and serve end nodes (EN) and low-entry networking (LEN) nodes directly attached to the network node. The domain of an APPN network node consists of itself and any end nodes for which it provides network services.

•APPN end nodes can access remote resources without requiring that those resources be configured on the end node. An end node can communicate with adjacent nodes on its own, but requires the services of a network node server to access nonadjacent nodes. The domain of an APPN end node includes only itself.

•Low-entry networking nodes (LEN nodes) are type 2.1 nodes that do not support APPN functions. They can communicate with adjacent nodes in an APPN network, but do not participate in the APPN network. In a LEN node, all potential sessions with remote LUs must be predefined, either specifically or through a single default entry indicating that all remote LUs reside in an adjacent network node that can be accessed using a certain link. The domain of a LEN node includes only itself.

For more information about peer-oriented node types, see “APPN Node Types”.

Connectivity

For two nodes to communicate, each node must have a combination of hardware and software that supports data flow between the nodes. The hardware component consists of an adapter at each node and the transmission medium that connects the two adapters. The software component provides control of the hardware and the data exchanged over it.

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Chapter 1