Ramblings & ephemera

Windows directory services

From David HM Spector’s Unfinished Business Part 2: Closing the Circle (LinuxDevCenter: 7 July 2003):

… an integrated enterprise directory service does give network managers a much greater ability to manage large-scale networks and resources from almost every perspective.

Unlike most UNIX systems, Windows environments are homogeneous. There are three modes of operation in terms of user and resource management in the Windows universe:

1. Stand-alone.
2. Domain membership through a domain controller.
3. Organizational-unit membership in an LDAP-based directory such as Active Directory (or via a third-party directory such as NDS, but those are declining as more organizations switch to AD). …

Three major pieces of software make up the bulk of what Active Directory does:

* LDAP, the Lightweight Directory Access Protocol.
* Kerberos, the authorization system originally developed as part of MIT Athena (later, the basis for the security components in OSF’s DME).
* A SQL database.

These components interact with the Windows APIs to deliver a one-stop repository for any attribute that can be used to describe a system, a service, a device, users, groups, a relationship, a policy, an authorization, or another relationship in a computing environment. …

LDAP in AD is used to manage:

* DNS addresses
* Workstation and server descriptions
* Printers
* Print queues
* Volume mappings
* Certificates
* Licenses
* Policies (such as ACLs, security policies, etc.)
* Groups
* Users
* Contacts

All of these data are stored in one unified system, which can be broken down relatively easily (with some major caveats) by physical location (site), division, organization unit, or department and workgroup, and managed in a distributed fashion. These data can be replicated for redundancy and performance purposes. All Windows APIs must operate within this system if they are to participate in the network and have access to its resources. Repository data is wrapped up by and authenticated through the use of Kerberos Tickets, which makes the system (again, general Windows caveats applied) secure. …

The most interesting part of this story is that 95% of the hard work has already been done! Microsoft didn’t invent totally new LDAP schemas to make Active Directory as comprehensive as it is — as usual, they embraced and extended the work of others. LDAP schemas already exist, and are publicly available to cover:

* Contact management: The InetOrgPerson schema
* IP Addresses, Users, Server/Workstation Info: The NIS schema
* Kerberos tickets: IETF Kerberos KDC schema

Of course, Microsoft’s own schemas are available for perusal on any Active Directory server (or, if you happen to have a Macintosh OS X box, look in /etc/openldap, for all of Microsoft’s schemas are there). …

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