Locate resource: SLU-initiated session

Figure 1. Locate resource: SLU-initiated session

The end node sends a session request for a primary LU (PLU) to its network node server. NN1 looks for the PLU in its directory database. NN1 has knowledge in the directory database that the PLU resides on EN2, which is served by NN3.
The network node sends a directed search request to NN3. Because NN1 does not have direct CP-CP sessions with NN3, NN1 sends the directed search request to NN3 through NN2.
NN2 is not the destination of the directed search; therefore, NN2 forwards the request to NN3.
NN3 receives the request and forwards it to EN2.
The APPN CP sends a SESS_REQ signal to the subarea SSCP.
The PLU initiates a search for the secondary LU (SLU), indicating that the location of the target does not have to be verified but that an RSCV must be calculated.
The end node sends a search request for the SLU to its network node server.
NN3 looks for the SLU in its directory database. NN3 has knowledge in its directory database that the SLU resides on EN1. Further, NN3 has information that allows the search to succeed without verifying the location of the SLU. On behalf of EN1, NN3 returns a positive reply, which includes the RSCV for the session.
The APPN CP replies to the subarea SSCP for the PLU-initiated request.
The subarea SSCP replies to the APPN CP for the SLU-initiated request, indicating that the session is already active.
The end node sends a reply for the SLU-initiated request to NN3.
NN3 replies to NN2.
NN2 replies to NN1.
NN1 replies to EN1.
The APPN CP replies to the subarea SSCP.