Advanced Peer to Peer Network. IBM network architecture for building dynamic routing across arbitrary network topologies. Intended as an eventual replacement for SNA, IBM's static routed, hierarchical network architecture.
An extension to SNA which routes information around the IBM network without help from the host, allowing systems to adjust dynamically to the topology of the network (dynamic routing). APPN keeps track of network topology, making it easier to connect and reconfigure. It also creates a directory of network nodes and other resources. APPN also allows for dynamic SNA networks, where nodes can join and leave the network as required, and session routes can be selected as needed.