Distributed Computing

DED BY:-BISWA RANJAN NAYAK

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SUMIT KUMAR REGD.NO:0601289144 1

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INTRODUCTION:A distributed system is one in which hardware or software components located at networked computers communicate and coordinate their actions only by message passing.  In the term distributed computing, the word distributed means spread out across space. Thus, distributed computing is an activity performed on a spatially distributed system. 

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These networked computers may be in the same room, same campus, same country, or in different continents 08/14/09

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Agent

Agent

Cooperation

Agent

Cooperation Distribution

Distribution

Cooperation

Distribution Agent

Internet Distribution

Subscription Job Request

Resource Management 08/14/09

Large-scale Application 4

Rise of Distributed Systems:

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Computer hardware prices are falling and power increasing. Network connectivity is increasing. Everyone is connected with fat pipes. It is easy to connect hardware together. Combination of cheap processors often more cost-effective than one expensive fast system. Flexibility to add according to needs. Potential increase of reliability. Sharing of resources.

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Characteristics of Distributed Computing:Parallel activities

Autonomous components executing concurrent tasks

Communication via message passing No shared memory.

Resource sharing

Printer, database, other services

No global state

No single process can have knowledge of the current global state of the system

No global clock

Only limited precision for processes to synchronize their clocks

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Characteristics of Distributed Computing(Cont.):Communication, failure handling, synchronization Protection, security Resource management (allocation of process, devices, memory, re-allocation) Naming (of resources, locating) Data management (files, sharing) Deadlock 08/14/09

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Distributed Computing Paradigms:The Message Passing Paradigm:Message passing is the most fundamental paradigm for distributed applications. A process sends a message representing a request. The message is delivered to a receiver, which processes the request, and sends a message in response. In turn, the reply may trigger a further request, which leads to a subsequent reply, and so forth.

PROCESS A

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PROCESS B

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The Client-Server Paradigm:Simple in concept, the client-server model provides an efficient abstraction for the delivery of network services. Operations required include those for a server process to listen and to accept requests, and for a client process to issue requests and accept responses. By assigning asymmetric roles to the two sides, event synchronization is simplified: the server process waits for requests, and the client in turn waits for responses. Many Internet services are client-server applications. These services are often known by the protocol that the application implements. Well known Internet services include HTTP , FTP, DNS,etc.

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SERVER HOST CLIENT HOST

SERVER PROCESS CLIENT PROCESS

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A SERVICE SERVICE REQUEST

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The Peer-to-Peer System Architecture:An architecture where computer resources and services are direct exchanged between computer systems. Resources and services include the exchange of information, processing cycles, cache storage, and disk storage for files. Computers that have traditionally been used solely as clients communicate directly among themselves and can act as both clients and servers, assuming whatever role is most efficient for the network. PROCESS 1 REQUEST

RESPONSE

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Application of Distributed Computing:Distributed Computing Using Mobile Programs:-

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Local Intranet:-

Internet:-

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JAVA RMI:Communicating Entities: Implementing some application for user

 Using support of distributed services  Layers of support  Client/server  Embedded in language Java: Object variant of remote procedure call  Adds naming compared with RPC  Restricted to Java environments

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JAVA RMI ARCHITECTURE:-

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Advantages:Economics:-

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Computers harnessed together give price/performance ratio than mainframes.

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Speed:-

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A distributed system may have computing power than a mainframe.

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Reliability:-

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Some applications are inherently distributed. E.g., an ATM-banking application.

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more

better

Inherent distribution of applications:-

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If one machine crashes, the system as a whole can still survive if you have multiple server machines and multiple storage devices (redundancy).

Extensibility and Incremental Growth:-

Possible to gradually scale up (in terms of processing power and functionality) by adding more sources (both hardware and software). This can be 17 done without disruption to the rest of the system.

Disadvantages:Lack of experience in designing, and implementing a distributed system. E.g. which platform (hardware and OS) to use, which language to use etc. But this is changing now. If the network underlying a distributed system saturates or goes down, then the distributed system will be effectively disabled thus negating most of the advantages of the distributed system. Security is a major hazard since easy access to data means easy access to secret data as well.

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Conclusion:In this world of optimization everybody is trying to get the optimized output from their limited resources. The concept of distributed computing is the most efficient way to achieve the optimization. In case of distributed computing the actual task is modularized and is distributed among various computer systems. It not only increases the efficiency of the task but also reduces the total time required to complete the task. Now the advanced concept of this distributed computing , that is distributed computing through mobile agent is setting a new landmark in this technology. A mobile agent is a process that can transport it’s state from one environment to another, with it’s data intact, and can be capable of performing appropriately in the new environment.

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Reference:Andrews, Gregory R. (2000), Foundations of Multithreaded, Parallel, and Distributed Programming, Addison–Wesley, ISBN 0-201-35752-6. Arora, Sanjeev; Barak, Boaz Complexity – A Modern ISBN 978-0-521-42426-4.

(2009), Computational Approach, Cambridge,

Cormen, Thomas H.; Leiserson, Charles E.; Rivest, Ronald L. (1990), Introduction to Algorithms (1st ed.), MIT Press, ISBN 0-262-03141-8. Dolev, Shlomi (2000), Self-Stabilization, MIT Press, ISBN 0-262-04178-2

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