Session initiation and INQUIRE APPSTAT requests are routed from the originating LU SSCP to the destination LU SSCP using trial-and-error routing. There are several different means of determining the list of adjacent SSCPs to try when performing trial-and-error routing. However, after the list is determined, the processing is very similar for each of these requests. The rules for routing session requests are as follows:

• The request is not routed if its visit count (SSCP rerouting count) is 0.
• The request is never routed back to the SSCP from which it was received.
• The request is never routed back to its originating SSCP.
• The request is never routed in this network if it was received from an SSCP in this network.
• The request is never routed back to the network from which it was received through the same gateway NCP.