X.500
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X.500 is a series of computer networking standards covering electronic directory services. The X.500 series was developed by ITU-T, formerly known as CCITT. The directory services were developed in order to support the requirements of X.400 electronic mail exchange and name lookup. ISO was a partner in developing the standards, incorporating them into the Open Systems Interconnect suite of protocols. ISO/IEC 9594 is the corresponding ISO identification.
The protocols defined by X.500 include:
- DAP (Directory Access Protocol)
- DSP (Directory System Protocol)
- DISP (Directory Information Shadowing Protocol)
- DOP (Directory Operational Bindings Management Protocol)
X.509, the portion of the standard providing for an authentication framework, is now also widely used outside of the X.500 directory protocols. It specifies a standard format for public-key certificates.
Because these protocols utilized the OSI networking stack, a number of alternatives to DAP were developed to allow Internet clients to access to the X.500 Directory using the TCP/IP networking stack. The most well-known alternative to DAP is Lightweight Directory Access Protocol (LDAP). While DAP and X.500 protocols can now utilize the TCP/IP networking stack, LDAP remains a popular directory access protocol.
List of X.500 series standards
| ITU-T number | ISO/IEC number | Title of Standard |
|---|---|---|
| X.500 | ISO/IEC 9594-1 | The Directory: Overview of concepts, models and services |
| X.501 | ISO/IEC 9594-2 | The Directory: Models |
| X.509 | ISO/IEC 9594-8 | The Directory: Authentication framework |
| X.511 | ISO/IEC 9594-3 | The Directory: Abstract service definition |
| X.518 | ISO/IEC 9594-4 | The Directory: Procedures for distributed operation |
| X.519 | ISO/IEC 9594-5 | The Directory: Protocol specifications |
| X.520 | ISO/IEC 9594-6 | The Directory: Selected attribute types |
| X.521 | ISO/IEC 9594-7 | The Directory: Selected object classes |
| X.525 | ISO/IEC 9594-9 | The Directory: Replication |
| X.530 | ISO/IEC 9594-10 | The Directory: Use of systems management for administration of the Directory |