This Recommendation describes the ISDN User Part signalling procedures of the set-up and clear down of national and international ISDN connections used for ISUP 2000. Actions common for all types of exchanges are described only once. Different or additional actions required in an exchange are specified in a separate subclause applicable to that type of exchange. The procedures specified in clause 2 relate to basic call (i.e. calls not involving supplementary services and IN).