This Recommendation describes Capability Set 2 (CS-2) of Bearer Independent Call Control (BICC) basic call procedures for the support of narrow-band ISDN services independent of the bearer technology and signalling message transport technology used. This Recommendation defines the procedures at the Call Service Functions (CSFs) within originating/destination Serving Nodes (SNs) (ISNs interworking with an access signalling system), intermediate national/international SNs (TSNs), incoming/outgoing nationalhnternational gateway SNs (GSNs) and Call Mediation Nodes (CMNs). Actions common for all types of SN/CMN are described once. Different or additional actions required at a specific type of SN/CMN are specified in a separate clause. ITU-T Q. 1902.1 provides an overview of the BICC protocol.