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The '''Distributed Computing Environment (DCE)''' is a software system developed in the early 1990s by a consortium that included [[Apollo Computer]] (later part of [[Hewlett-Packard]]), [[IBM]], [[Digital Equipment Corporation]], and others.
==History==
DCE came about to a large degree as part of the [[Unix wars]] of the 1980s. After [[Sun Microsystems]] and [[AT&T]] worked together to produce [[UNIX System V|UNIX System V Release 4]] (SVR4), many of the other Unix vendors felt their market was unduely disadvantaged. They quickly formed the [[Open Software Foundation]] (OSF) to compete with a [[BSD]]-based Unix that more closely matched their own offerings. OSF ended up introducing [[OSF/1]], which was based on the [[Mach kernel]] and had relatively poor performance compared to SVR4, and was little used except by DEC.
As a side effect of the formation of OSF, the various members also contributed many of their ongoing research projects. At the time, network computing was "all the rage", and many of the companies involved were working on similar RPC-based systems. By re-building these various utilities on a single "official" RPC mechanism, OSF could offer a major advantage over SVR4, allowing any DCE-supporting system (namely OSF/1) to interoperate in a larger network.
The largest unit of management in DCE is a cell. The highest privileges within a cell are assigned to a role called cell administrator. Typically this privileges are held by a DCE principal called cell_admin. Note that this need not be a real OS-level user. The cell_admin has all privileges over all DCE resources within the cell. Privileges can be awarded to or removed from the following categories : user_obj, group_obj, other_obj, any_other for any given DCE resource. The first three correspond to the owner, group member, and any other DCE principal respectively. The last group contains any non-DCE principal. Multiple cells can be configured to communicate and share resources with each other. All principals from external cells are treated as "foreign" users and privileges can be awarded / removed accordingly. In addition to this, specific users or groups can be assigned privileges on any DCE resource - something which is not possible with the traditional UNIX filesystem.▼
The DCE system was, to a large degree, based on independant developments made by each of the partners. DCE/RPC was derived from the [[Network Computing System]] (NCS) created at Apollo Computer. The naming service was derived from work done at DEC. DCE/DFS was based on the [[Andrew file system]] (AFS) originally developed at [[Carnegie Mellon University]]. The authentication system was based on [[Kerberos]], and the authorization system based on [[Access Control List]]s (ACL's). By combining these features, DCE offers a fairly complete [[C programming language|C]]-based system for network computing. Any machine on the network can authenticate its users, gain access to resources, and then call them remotely using a single integrated [[API]].
Distributed computing never really "caught on" as it had been hoped in the late-80s and early '90s. The rise of the [[internet]], [[Java programming language|Java]] and [[web services]] stole much of its [[mindshare]] through the mid-to-late 1990s, and competing systems such as [[CORBA]] muddied the waters as well. Perhaps ironically, one of the major uses of DCE/RPC today is [[Microsoft]]'s [[DCOM]] and [[ODBC]] systems, which use DCE/RPC as their network transport layer.
The Open Group released DCE 1.2.2 under a [[free software license]] (the [[GNU Lesser General Public License|LGPL]]) on [[12 January]] [[2005]]. DCE 1.1 was available much earlier under the OSF BSD license, and resulted in FreeDCE[http://freedce.sf.net] being available since 2000. FreeDCE contains an implementation of DCOM.
==Description==
▲The largest unit of management in DCE is a '''cell'''. The highest privileges within a cell are assigned to a role called ''cell administrator
There are three major components of DCE within every cell: (1) the security server (which is responsible for authentication) (2) The Cell Directory Server (CDS) (which is the respository of resources and ACLs) and (3) The Distributed Time Server which provides an accurate clock for proper functioning of the entire cell. Modern DCE implementations such as IBM's are fully capable of interoperating with Kerberos as the security server, LDAP for the CDS and the [[Network Time Protocol]] implementations for the time server.
While it is possible to implement a distributed file system using
DCE/DFS is believed to be the world's only distributed filesystem that correctly implements the full POSIX filesystem semantics
==External links==
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