Figure 1 shows
a connection between an IBM® 
iSeries™ system
in Minneapolis and an IBM iSeries system
in Madison over a frame-relay network.
The two systems have an Advanced Peer-to-Peer Networking (APPN) connection that is configured on the frame-relay data link connection identifier (DLCI). Note that the frame-relay link in Minneapolis has much more traffic and operates at 1 536 000 bps. The link in Madison operates at 64 000 bps. The frame-relay network allows for this difference in subscriptions at the two sites.
The Minneapolis connection to the network uses DLCI 23. In Madison, the DLCI number is 21. If the connection uses a frame-relay network, the DLCI numbers have only local (terminal end (TE) to frame handler (FH)) significance and might be different on the two interfaces. The network is responsible for setting up the connection between the DLCIs at administration time.
If you require more than one Advanced Program-to-Program Communication (APPC) connection between the two sites, you must define additional source service access point (SSAP) and destination service access point (DSAP) values on the lines, and the additional controllers need different SSAP and DSAP combinations.