Distributed Computing Environment: Difference between revisions

Revision as of 20:53, 7 August 2005

Revision as of 01:03, 27 August 2005

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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, an [[authentication]] service, and a [[distributed file system]] (DFS). [[DCE /RPC]] was derived from an earlier RPC system called 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]], and later extended by Transarc Corporation (which was later merged into IBM). DCE 1.2.2 was released on 12th January 2005 under a [[free software license]] (the [[GNU Lesser General Public License|LGPL]]) by [[The Open Group]]. 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.

To understand why DCE is useful, one must look at its closest competitor - [[Kerberos (protocol)|Kerberos]]. Like DCE, Kerberos is a distributed computing application. It provides an authentication system for a network of machines - much like Sun's [[Network Information Service]] or [[LDAP]]. Kerberos is an authentication system only - it can identify the entity requesting resources to the server, but it cannot do authorization. That has to be implemented at each individual server. If for example, in a system that uses Kerberos authentication, a user A authenticates himself and requests resource R on machine M1, then M1 has to be set up to authorize A to access R on M1. If R is a shared resource thats available on machine M2 also, then M2 has to explicitly authorize A to access resource R. Kerberos does not provide a way to allow one to share authorization settings across its ___domain. DCE can. It does this by supporting [[Access Control List]]s (ACLs).