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Distributed Computing Environment


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									Distributed Computing Environment (DCE)

              Advanced Operating Systems (8320)

                                   Pradeep Konduri
   What is DCE?
   DCE Architecture
   Some models
   References
   The DCE is a software that supplies a framework and
    toolkit for developing client/server applications. The
    framework includes a Remote Procedure Call (RPC)
    mechanism, a naming (directory) service, a time
    service, an authentication service, an authorization
    service and a Distributed File System.

   DCE runs on all major computing platforms and is
    designed to support distributed applications in
    heterogeneous hardware and software environments.
    DCE is a key technology in three of today's most
    important areas of computing: security, the World Wide
    Web, and distributed objects.
   Largest management unit in DCE is cell.
   The highest privileges within a cell are assigned to a role called cell
   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 Access Control
         Lists and

     •   The Distributed Time Server that provides an accurate clock for proper functioning of the
         entire cell.
The DCE infrastructure supports the
construction and integration of client/server
applications while attempting to hide the
inherent complexity of the distributed
processing from the user [Schill 93].

The OSF DCE is intended to form a
comprehensive software platform on which
distributed applications can be built, executed,
and maintained.
   Fundamental distributed services provide tools for software developers to create the
    end-user services needed for distributed computing. They include

     •   Remote Procedure Call, which provides portability, network independence, and secure distributed
     •   Directory services, which provides a single naming model to allow programmers and maintainers to
         identify and access distributed resources more easily.
     •   Time service, which provides a mechanism to monitor and track clocks in a distributed environment and
         accurate time stamps to reduce the load on system administrator.
     •   Security service, which provides the network with authentication, authorization, and user account
         management services to maintain the integrity, privacy, and authenticity of the distributed system.
     •   Thread service, which provides a simple, portable, programming model for building concurrent

   Data-sharing services provide end users with capabilities built upon the fundamental
    distributed services. These services require no programming on the part of the end user
    and facilitate better use of information. They include

     •   Distributed file system, which interoperates with the network file system to provide a high-performance,
         scalable, and secure file access system.
     •   Diskless support, which allows low-cost workstations to use disks on servers, possibly reducing the
         need/cost for local disks, and provides performance enhancements to reduce network overhead.

          Distributed Services
Concurrency control, group management, etc

   Distributed File Service

          Basic System Services
     Time, name, process services, etc

 RPC and Group Communication

      Processes and Threads

  Kernel with transport service
Open Grid Services Architecture

      Based upon Web Services (ports that are service endpoints)
      Web Services Description Language: XML language used to describe Web Service
      Universal Description Discovery and Integration: Mechanism needed to discover Web
      APIs that can be accessed over a network, such as the Internet, and executed on a remote
       system hosting the requested services.
      P2P
   Design Issues
      Interoperability between implementations
      Extensibility not standardized
      Usability questionability
   United Devices Grid MP
     • Design
        Web Services Based
        Grid MP system consists of a set of servers providing grid services
        Grid MP resources run a lightweight Agent
     • Architecture
        Multi-Tiered (P2P) or Client/Server
         Batch Jobs
         MPI Jobs
         Data-parallel jobs
   Design Issues
     • Resource Discovery-Unreliable resources
     • Replication-Same job executing on multiple machines
   Fine Grained Cycle Sharing
         Based on Web Services
         Uses Resource Description Framework (RDF): An evolutionary stage of the World
          WideWeb in which automated software can store, exchange, and use machine-
          readable information distributed throughout the web
         APIs
         Multi-Tiered (P2P)
      Design Issues
         Failure Recovery
         Coherency
   Distributed Operating Systems & Algorithms, Randy Chow and Theodore Johnson, Addison Wesley,
   Distributed Systems principles and paradigms by Andrew S. Tanenbaum, Maarten van Steen, 2002
    Kim, K.H., "APIs for Real-Time Distributed Object Programming", IEEE Computer, June 2000, pp.72-80.
   Resource Availability Prediction in Fine-Grained Cycle Sharing, Xiaojuan Ren, Seyong Lee, Rudolf
    Eigenmann, Saurabh Bagchi, Systems. HPDC'06, Paris, France. June, 2006
   Developing the Distributed-Computing OS, Vaughan-Nichols, S.J.; Computer Volume 35, Issue 9, Sept.
    2002 Page(s):19 - 21
   Kim, J. Thuraisingham, B. Object and Component-Oriented Real-Time Distributed Computing, 2007.
    ISORC '07.
Thank you

      --Pradeep Konduri

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