Session parameters and subarea Class of Service are determined in the SSCP that is closest to the secondary logical unit (SLU). This includes cases where this VTAM®:

• Owns the SLU (the SLU is an application or a dependent LU in this VTAM domain), like HostD owns LUD in Figure 1
• Owns the boundary function in the direction of an LEN-attached independent SLU, like HostD does for LUD in Figure 1
• Owns the boundary function in the direction of an APPN-attached independent SLU, like HostA does for LUD in Figure 1. This VTAM might:
  • Own the primary logical unit (PLU), and the SLU is elsewhere in (or through) the APPN network.
  • Be an interchange node, with the PLU in (or through) the subarea network, and the SLU elsewhere in (or through) the APPN network.
  • Be part of a composite network node that is an intermediate node on the BIND path of the session. In this case, the Class of Service is needed to determine the subarea route through the composite network node.