ITU-T Recommendation Q.2931 provides basic call and connection control for point-to-point connections in a B-ISDN. This amendment to ITU-T Recommendation Q.2931 has been prepared to reflect changes, clarifications and additions to the basic call/connection control messages and procedures of DSS2. The changes are based on errors and inconsistencies identified in ITU-T Recommendation Q.2931 since its first publication in 1995. This amendment is designed to be compatible with implementations conforming to ITU-T Recommendation Q.2931 (02/95) and Amendments 1, 2 and 3 to ITU-T Q.2931.