Ldap Servers

by Remko van Dokkum

Ldap Servers

What is LDAP server?

Directory service (LDAP server) is a software system that stores, organizes and provides access to information in a directory; a shared information infrastructure for locating, managing, administering, and organizing common items and network resources, which can include volumes, folders, files, printers, users, groups, devices, telephone numbers and other objects. To access directories servers and clients interact in the model of client/server communication. The process of directory access happens in the following way: a directory client calls API (application programming interface) to access a directory for reading or writing the information. The client call accesses the information in the directory on behalf of the requesting client via TCP/IP (the default LDAP TCP/IP ports – 636 for secure communications, 389 for unencrypted communications). The results of the action are returned to the client then. Servers provide a specific service to LDAP clients. Sometimes directory servers may become the clients of other servers to collect the necessary information for request processing.
LDAP server performs the following basic operations:

Search entries;
Compare entries;
Add entries;
Delete entries;
Modify entries;
Move entries;
Rename entries;
Extended operation;
Authentication.

According to X.500 standard, servers can be connected into a hierarchical structure. That is why users can proceed from one server to another while searching the necessary information. Web interface is widely used for server administration including remote administration.
Directory services can be used for:

Locating and providing information about people (address books, yellow pages, white pages) and distributed resources like printers;
User authentication and authorization for Web servers or other LDAP-enabled applications;
Policies that are shared by multiple applications or application instances.

Directory server main components are:

A front-end (handles LDAP client operations coming into the server over TCP/IP connection);
A database back-end (handles stores and retrieves directory objects from relational database).

Some researchers and professionals highlight the best LDAP servers from the number of open source and commercial ones:
Open source LDAP servers include:

Red Hat Directory Server/Fedora Directory Server. Red Hat Directory Server was initially bought from Netscape Security Solutions as a commercial product for Red Hat Enterprise Linux. Nowadays it is produced by Red Hat with name Red Hat Directory Server. Following its policy Red Hat produced version for Fedora Core also. It is called Fedora Directory Server that is perfect for distributives on the basis of RedHat. Codes of these servers coincide greatly because of the common root. Unlike OpenLDAP Fedora/Red Hat directory servers have good documentation.
OpenLDAP. OpenLDAP is the further development of the original slapd. It is widely distributed and used on many platforms like Linux, FreeBSD, Windows and MacOS X. Documentation containing on the website is quite obsolete, but there are many useful step-by-step instructions. OpenLDAP is time-tested. Its functionality is practically identical to RedHat directory server.

Commercial LDAP Servers are:

Novell eDirectory. All products are free for higher educational establishments. It works with the help of the following operational systems: Novell Netware, Windows (NT), Linux (SUSE Enterprise, or RedHat), Solaris, AIX, HP-UX. You have everything in one product – all the necessary programs are given at once. Installation and customization are easy. Advantages – exclusive documentation and affordable price, technical support for registered users and cross-platform function. Disadvantage – closed source files.
Microsoft Active Directory. It is a part of Windows Server family. It’s a perfect solution for MS networks. Advantages – perfect integration into the system, highly qualified documentation.
Sun Java System Directory Server. Sun merged with IPlanet Company and created its new product – Sun ONE, renamed afterwards to Sun Java System Directory Server. It is not a standalone product, but just a part of Java Enterprise System. System requirements: Solaris 10, Solaris 9, Solaris 8 (only for SPARC), Red Hat Enterprise Linux 2.1 and 3.1, HP-UX 11i, Microsoft Windows 2000, XP, 2003. You can not buy it apart from Java Enterprise System. But if you decide to use complex solution from Sun, you won’t have any problems. Sun engineers will help you to install and configure it according to your requirements.
IBM Tivoli Directory Server. LDAP-solution from IBM. It is supported by the following operational systems: AIX, Solaris, Microsoft Windows 2000, HP-UX, and also Linux for Intel and IBM eServer iSeries, pSeries and zSeries. Advantage – qualified, open and free for all documentation.

LDAP servers cannot access directories without LDAP clients. Some of them are presented below:
Microsoft Windows:

Softerra LDAP Administrator/LDAP Browser;
LDAPSoft LDAP Browser/LDAP Admin Tool;
LDAPAdmin;
MaXware Directory Explorer;
Active Directory Explorer

Linux/UNIX

Evolution;
KAddressBook;
LDAPSoft LDAP Browser/Administrator.

Mac OS X

Address Book;
Directory Access;
Workgroup Manager.

Cross-platform:

Apache Directory Studio;
Ekiga (formerly GnomeMeeting);
Mozilla Thunderbird;
Novell Evolution;
phpLDAPadmin.

Storing data in a directory and sharing it amongst applications saves you time and money by keeping administration effort and system resources down.

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