When the network comes up, the LU is assigned a network address consisting of a subarea number and a station number. Each NCP governs a subarea. However, the APPN network does not have global addresses. A session is established by sending a BIND through the network from the client to the server. As the BIND flows, each intermediate node assigns a numeric ID to the session itself, with control blocks indicating the routing of messages on the session in each direction.
Subsequent traffic is routed by the session number.
Neither the client, the server, nor any node in the middle has any global view of the source or destination of any of the messages. There are no NAU's in an APPN network. For an emulated 3270 display or printer, Logical Units are identified by a one byte number, not by their name. For a desktop system that will only be a client to other systems, it is necessary to have one LU, but the name does not matter. Other workstation systems may require an explicit configuration step with some chosen name.