Advanced Peer-to-Peer Networking

In 1981, IBM began to introduce communication standards that developed into a peer-oriented network architecture called Advanced Peer-to-Peer Networking (APPN). The development of APPN marks a significant change from the traditional top-down hierarchical SNA model because APPN supports a form of distributed processing. That is, all computers on an APPN network can communicate directly with each other, without having to depend on centralized type 5 hosts or type 4 communications controllers. This model provides an environment that is more flexible than the traditional top-down hierarchical model.

APPN defines how peer-oriented components communicate with each other, as well as the level of network services, such as routing sessions, that are supplied by each computer on the network.

The SNA APPN model defines its own standards for the following components:

Hardware Components or Nodes    Hardware that provides the computing platforms and network devices that implement specific SNA APPN communications and management functions.

Connection Types    Hardware and communication standards that provide the data communication paths between components in an SNA APPN network.

Physical Units (PUs)    Hardware and software that provide the configuration support and control of the SNA APPN network devices, connections, and protocols.

Logical Units (LUs)    Protocols that provide a standardized format for delivery of data for specific applications, such as terminal access and printing.

Note

Although the SNA APPN network model is organized into the same component classes as the hierarchical SNA network model, the components themselves are often quite different from the components used in the hierarchical model.

The following sections describe each of these components and how they interact in an SNA APPN environment.