In SNA, a subarea node that provides protocol support for adjacent peripheral nodes, for example, transforming network addresses to local addresses and vice versa, and providing session-level support for these peripheral nodes. In XRF, the point at which terminal sessions are switched from the failing active system to the new active system. The communication controller (or, in CICS/VSE, an XSWITCH mechanism) at the BNN must be able to operate in an XRF configuration.