technologi komputer

Kamis, 07 Juli 2011

About Distributed Computing Environment

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The Details of the basic services are hidden from end users. Distributed Computing Environment is an open system that can run on any platform or operating system. It is not restricted to UNIX. The Distributed computing Environment model provides an integrated approach to distributed processing. Its layer architecture provides flexibility to include future technologies. Each layer provides its own security and management.

Distributed Computing Environment provides two sets of services:
Basic Distributed services allow developers to build applications.
• Data- Sharing services, which require no programming by the end users, include a distributed file system, disk-less system support, and micro integration.

The tools provided by Distributed Computing Environment as basic Distributed services are:
Remote procedure calls
• Distributed Directory Service
• Threads Service
• Time Service
• Security Service

Remote procedure Calls:
Distributed computing Environment's remote procedure calls allow an application's program to execute on more than one server in the network, regardless of the other machines' architectures or physical locations. Because information transfer is transparent between different platforms, the use of remote procedure calls allows heterogeneous operation.
Distributed Directory Service:
This service provides a single naming model throughout the distributed network. Users locate and access
servers, files or print queues by name, not their physical location. Users use the same name even if the networks address changes. The Directory services use a local cell directory service and a global directory service. Global names can reside in the X.500 standard directory service or Internet Domain Name System name space.

Threads Service:
Distributed Computing Environment requires for operation. The Threads Services allows multiple threads of execution in a single process and synchronizes the global data access. One thread can be executing a remote procedure call, while another processes user input. Applications do not need to know whether threads are executing on one or several processors.
Time Service:
This software-based service synchronizes system clocks among host computers in both local area network and wide area network environments. It provides an accurate time stamp for application development files that must be stored in sequence. The Time Services also supports time values from external services used for distributed sites using the Network Time Protocol.
Security Service:
Data integrity and privacy by three facilities:
• Authentication is based on the Kerberos version 5 standards from MIT. It verifies a user through a third server.
• Once users are authenticated, the authorization facility decides if they should have access to the requested resources.
• A user registry facilities the management of user information, the registry ensures that user names are unique across the network.

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