In the peer-oriented SNA network model, all computers on the network can communicate directly with each other. Advanced Peer-to-Peer Networking (APPN) is the architecture developed by IBM that enables distributed data processing. APPN defines how components communicate with each other, and the level of network-related services, like routing sessions, that are supplied by each computer in the network.
Figure 4.7 Connections in a peer-oriented network.
In an APPN network, SNA Server emulates a type 2.1 physical unit device (PU 2.1). SNA Server computers can connect to an AS/400 using several connection methods:
Frame relay or bridging solutions can also be implemented to transport SNA traffic over WAN connections in branch-based deployment models. SNA Server operates as an APPN Low-Entry Networking (LEN) node and communicates with other APPN nodes using the Advanced Program-to-Program Communications (APPC) or LU 6.2 protocol.