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Directory service

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In computing , a directory service or name service maps the names of network resources to their respective network addresses . It is a shared information infrastructure for locating, managing, administering and organizing everyday items and network resources, which can include volumes, folders, files, printers, users, groups, devices, telephone numbers and other objects. A directory service is a critical component of a network operating system . A directory server or name server is a server which provides such a service. Each resource on the network is considered an object by the directory server. Information about a particular resource is stored as a collection of attributes associated with that resource or object.

A directory service defines a namespace for the network. The namespace is used to assign a name (unique identifier) to each of the objects. Directories typically have a set of rules determining how network resources are named and identified, which usually includes a requirement that the identifiers be unique and unambiguous . When using a directory service, a user does not have to remember the physical address of a network resource; providing a name locates the resource. Some directory services include access control provisions, limiting the availability of directory information to authorized users .

Comparison with relational databases [ edit ]

Several things distinguish a directory service from a relational database . Data can be made redundant if it aids performance (e.g. by repeating values through rows in a table instead of relating them to the contents of a different table through a key, which technique is called denormalization ; another technique could be the utilization of replicas for increasing actual throughput). [1]

Directory schemas are object classes, attributes, name bindings and knowledge (namespaces) where an object class has:

  • Must - attributes that each instances must have
  • May - attributes which can be defined for an instance but can be omitted, with the absence similar to NULL in a relational database

Attributes are sometimes multi-valued, allowing multiple naming attributes at one level (such as machine type and serial number concatenation , or multiple phone numbers for "work phone"). Attributes and object classes are usually standardized throughout the industry; for example, X.500 attributes and classes are often formally registered with the IANA for their object ID. [ citation needed ] Therefore, directory applications try to reuse standard classes and attributes to maximize the benefit of existing directory-server software.

Object instances are slotted into namespaces; each object class inherits from its parent object class (and ultimately from the root of the hierarchy ), adding attributes to the must-may list. Directory services are often central to the security design of an IT system and have a correspondingly-fine granularity of access control.

Replication and distribution [ edit ]

Replication and distribution have distinct meanings in the design and management of a directory service. Replication is used to indicate that the same directory namespace (the same objects) are copied to another directory server for redundancy and throughput reasons; the replicated namespace is governed by the same authority. Distribution is used to indicate that multiple directory servers in different namespaces are interconnected to form a distributed directory service; each namespace can be governed by a different authority.

Implementations [ edit ]

Directory services were part of an Open Systems Interconnection (OSI) initiative for common network standards and multi-vendor interoperability. During the 1980s, the ITU and ISO created the X.500 set of standards for directory services, initially to support the requirements of inter-carrier electronic messaging and network-name lookup. The Lightweight Directory Access Protocol (LDAP) is based on the X.500 directory-information services, using the TCP/IP stack and an X.500 Directory Access Protocol (DAP) string-encoding scheme on the Internet .

Systems developed before the X.500 include:

  • Domain Name System (DNS): The first directory service on the Internet, [2] still in use
  • Hesiod : Based on DNS and used at MIT's Project Athena
  • Network Information Service (NIS): Originally Yellow Pages (YP) Sun Microsystems ' implementation of a directory service for Unix network environments. It played a role similar to Hesiod.
  • NetInfo : Developed by NeXT during the late 1980s for NEXTSTEP . After its acquisition by Apple, it was released as open source and was the directory service for Mac OS X before it was deprecated for the LDAP-based Open Directory. Support for NetInfo was removed with the release of 10.5 Leopard.
  • Banyan VINES : First scalable directory service
  • NT Domains : Developed by Microsoft to provide directory services for Windows machines before the release of the LDAP-based Active Directory in Windows 2000. Windows Vista continues to support NT Domains after relaxing its minimum authentication protocols.

LDAP implementations [ edit ]

LDAP/X.500-based implementations include:

Open-source tools to create directory services include OpenLDAP, the Kerberos protocol and Samba software , which can function as a Windows domain controller with Kerberos and LDAP back ends . Administration is by GOsa or Samba SWAT.

Using name services [ edit ]

Unix systems [ edit ]

Name services on Unix systems are typically configured through nsswitch.conf . Information from name services can be retrieved with getent .

See also [ edit ]

References [ edit ]

Citations [ edit ]

  1. ^ "When and How You Should Denormalize a Relational Database" . rubygarage.org . Retrieved 2023-04-30 .
  2. ^ "RFC1034" . IETF.org. 1978-11-01 . Retrieved 2018-02-13 .
  3. ^ "Red Hat Spending $23 Million For Ex-Netscape Security Solutions Business" . Retrieved 2018-04-22 .
  4. ^ "Oracle and Sun" . Sun.com. 2010-09-07 . Retrieved 2012-01-09 .
  5. ^ "Java.net" . Opends.dev.java.net. Archived from the original on 2007-07-04 . Retrieved 2012-01-09 .
  6. ^ "ForgeRock has shuttered the open-source community, and no longer allows new development on their platform under a permissive license" . timeforafork . June 1, 2017. Archived from the original on October 3, 2017 . Retrieved June 1, 2017 .

Sources [ edit ]

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