This Recommendation / International Standard specifies the Directory Access Protocol, the Directory System Protocol, the Directory Information Shadowing Protocol, and the Directory Operational Binding Management Protocol fulfilling the abstract services specified in ITU-T Rec. X.511 ISO/IEC 9594-3, ITU-T Rec. X.518 ISO/IEC 9594-4, and ITU-T Rec. X.525 ISO/IEC 9594-9.