Editing Distributed Computing Environment

{{more citations needed|date=December 2011}}
The '''Distributed Computing Environment''' ('''DCE''') is a [[software system]] developed in the early 1990s from the work of the [[Open Software Foundation]] (OSF), a consortium founded in 1988 that included [[Apollo Computer]] (part of [[Hewlett-Packard]] from 1989), [[IBM]], [[Digital Equipment Corporation]], and others.<ref name="JiaZhou2004">{{cite book|author1=Weijia Jia|author2=Wanlei Zhou|title=Distributed Network Systems: From Concepts to Implementations|url=https://books.google.com/books?id=_pYyEgj0fX8C&pg=PA135|date=15 December 2004|publisher=Springer Science & Business Media|isbn=978-0-387-23839-5|page=135}}</ref><ref name="SINHA1998">{{cite book|author=PRADEEP K. SINHA|title=DISTRIBUTED OPERATING SYSTEMS: CONCEPTS AND DESIGN|url=https://books.google.com/books?id=SewHKWac2I4C&pg=PA35|date=1 January 1998|publisher=PHI Learning Pvt. Ltd.|isbn=978-81-203-1380-4|page=35}}</ref> The DCE supplies a [[software framework|framework]] and a toolkit for developing [[client/server]] applications.<ref name="Jacobsen2003">{{cite book|author=Hans-Arno Jacobsen|title=Distributed Infrastructure Support for Electronic Commerce Applications|url=https://books.google.com/books?id=9W8QkfzD0VYC&pg=PA14|date=30 November 2003|publisher=Springer Science & Business Media|isbn=978-1-4020-7648-0|page=14}}</ref> The framework includes:

* a [[remote procedure call]] (RPC) mechanism<ref name="change" /> known as [[DCE/RPC]]
* a naming ([[directory service|directory]]) service<ref name="change" />
* a time service<ref name="change" />
* an [[authentication]] service<ref name="change" />
* a [[distributed file system]] (DFS)<ref name="change" /> known as [[DCE Distributed File System|DCE/DFS]]
The DCE did not achieve commercial success.

As of 1995, all major computer hardware vendors had an implementation of DCE, seen as an advantage compared to alternatives like [[CORBA]] which all had more limited support.<ref name="change" />{{rp|13}}

==History==
As part of the formation of OSF, various members contributed many of their ongoing research projects as well as their commercial products. For example, HP/Apollo contributed its Network Computing Environment (NCS) and CMA Threads products.  Siemens Nixdorf contributed its X.500 server and ASN/1 compiler tools.  At the time, network computing was quite popular, and many of the companies involved were working on similar [[Remote procedure call|RPC]]-based systems. By integrating security, RPC and other distributed services on a single distributed computing environment, OSF could offer a major advantage over SVR4, allowing any DCE-supporting system (namely OSF/1) to interoperate in a larger network.

The DCE "request for technology" was issued by the OSF in 1989.
The first OSF DCE vendor product came out in 1992.<ref name="change" >
J. Mansfield and J. Clothier.
[https://apps.dtic.mil/sti/tr/pdf/ADA307256.pdf "Distributed Computing Environment: An Architecture for Supporting Change?"].
1995.
</ref>{{rp|3}}

The DCE system was, to a large degree, based on independent 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 Digital. DCE/DFS was based on the [[Andrew File System]] (AFS) originally developed at [[Carnegie Mellon University]]. The authentication system was based on [[Kerberos (protocol)|Kerberos]]. By combining these features, DCE offers a fairly complete system for network computing. Any machine on the network can authenticate its users, gain access to resources, and call them remotely using a single integrated [[Application Programming Interface|API]].

The rise of the [[Internet]], [[Java (programming language)|Java]] and [[web services]] stole much of DCE's [[mindshare]] through the mid-to-late 1990s, and competing systems such as [[CORBA]] appeared as well.

One of the major uses of DCE today is [[Microsoft]]'s [[Distributed Component Object Model|DCOM]] and [[ODBC]] systems, which use DCE/RPC (in [[MSRPC]]) as their network transport layer.{{Cn|date=December 2023}}

OSF and its projects eventually became part of [[The Open Group]], which released DCE 1.2.2 under a [[free software license]] (the [[GNU Lesser General Public License|LGPL]]) on 12 January 2005.<ref>
[https://www.iaps.com/DCE-open-source-announcement.html "DCE Open Source Licensing"].
2005.
</ref><ref>
[https://lwn.net/Articles/119042/ "DCE to be released under the LGPL"].
2005.
</ref>

DCE 1.1 was available much earlier under the OSF BSD license, and resulted in [[FreeDCE]] being available since 2000. FreeDCE contains an implementation of DCOM.<ref name="advogato" >
[https://web.archive.org/web/20170628063652/http://www.advogato.org/article/817.html "The Open Group releases DCE 1.2.2 as LGPL'd Free Software"].
</ref>

One of the major systems built on top of DCE was [[Encina (software)|Encina]], developed by [[Transarc]] (later acquired by [[IBM]]). IBM used Encina as a foundation to port its primary mainframe transaction processing system ([[CICS]]) to non-mainframe platforms, as [[IBM TXSeries]]. (However, later versions of TXSeries have removed the Encina component.)

==Architecture==

DCE is intended to support [[high availability]] systems: when a server does not respond (because of server failure or communications failure), clients can be constructed to automatically use a replica of that server instead.<ref name="change" />{{rp|11}}{{rp|21}}

The largest unit of management in DCE is a ''cell''. The highest privileges within a cell are assigned to a role called ''cell administrator'', normally assigned to the "user" ''cell_admin''. 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 or 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, which lacks ACL's.

Major components of DCE within every cell are:
#The Security Server that is responsible for authentication
#The Cell Directory Server (CDS) that is the repository of resources and ACLs and
#The Distributed Time Server that 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.

DCE/DFS is a DCE-based application which provides a distributed filesystem on DCE. DCE/DFS can support replicas of a fileset (the DCE/DFS equivalent of a filesystem) on multiple DFS servers - there is one read-write copy and zero or more read only copies. Replication is supported between the read-write and the read-only copies. In addition, DCE/DFS also supports what are called "backup" filesets, which if defined for a fileset are capable of storing a version of the fileset as it was prior to the last replication.

DCE/DFS is believed to be the world's only distributed filesystem that correctly implements the full POSIX filesystem semantics, including byte range locking.<ref name="advogato" />

DCE/DFS was sufficiently reliable and stable to be utilised by [[IBM]] to run the back-end filesystem for the 1996 [[Olympics]] web site, seamlessly and automatically distributed and edited worldwide in different time zones.<ref name="advogato" />

== References ==
{{reflist}}

==External links==
*[http://www.opengroup.org/dce/ The Open Group's DCE Portal]

{{Open Group standards}}

[[Category:Inter-process communication]]
[[Category:Internet Protocol based network software]]
[[Category:Open Group standards]]
[[Category:Distributed computing]]