Distributed Computing Environment: Difference between revisions

Revision as of 16:09, 17 December 2011

Revision as of 04:37, 1 May 2012

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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. The DCE supplies a framework and toolkit for developing [[client/server]] applications. The framework includes a [[remote procedure call]] (RPC) mechanism known as [[DCE/RPC]], a naming (directory) service, a time service, an [[authentication]] service and a [[distributed file system]] (DFS) known as [[DCE Distributed File System|DCE/DFS]].

DCE was a big step in direction to standardisation of architectures, which were manufacturer dependent before. Transforming the concept in software for different platforms has been given up after a short period. Similar to the [[OSI model]] DCE was not granted success, the underlying concepts however prevailed.

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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.

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. 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.

==Architecture==

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While it is possible to implement a distributed file system using the DCE underpinnings by adding filenames to the CDS and defining the appropriate ACLs on them, this is not user-friendly. 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. 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 timezones.

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