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Distributed Systems Architectures

This lecture covers different distributed systems architectures, including client-server, distributed object, peer-to-peer, and service-oriented models. Topics include advantages, disadvantages, middleware, and multiprocessor architectures.

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Distributed Systems Architectures

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  1. DistributedSystems Architectures IS301 – Software Engineering Lecture # 15 – 2004-10-04 M. E. Kabay, PhD, CISSP Assoc. Prof. Information AssuranceDivision of Business & Management, Norwich University mailto:mkabay@norwich.edu V: 802.479.7937

  2. Objectives • To explain the advantages and disadvantages of different distributed systems architectures • To discuss client-server and distributed object architectures • To describe object request brokers and the principles underlying the CORBA standards • To introduce peer-to-peer and service-oriented architectures as new models of distributed computing.

  3. Topics covered • Multiprocessor architectures • Client-server architectures • Distributed object architectures • Inter-organizational computing Today we will use 27 of Prof. Sommerville’s slides in class

  4. Distributed systems • Virtually all large computer-based systems are now distributed systems. • Information processing is distributed over several computers rather than confined to a single machine. • Distributed software engineering is therefore very important for enterprise computing systems.

  5. System types • Personal systems that are not distributed and that are designed to run on a personal computer or workstation. • Embedded systems that run on a single processor or on an integrated group of processors. • Distributed systems where the system software runs on a loosely integrated group of cooperating processors linked by a network.

  6. Distributed system characteristics • Resource sharing • Sharing of hardware and software resources. • Openness • Use of equipment and software from different vendors. • Concurrency • Concurrent processing to enhance performance. • Scalability • Increased throughput by adding new resources. • Fault tolerance • The ability to continue in operation after a fault has occurred.

  7. Distributed system disadvantages • Complexity • Typically, distributed systems are more complex than centralized systems. • Security • More susceptible to external attack. • Manageability • More effort required for system management. • Unpredictability • Unpredictable responses depending on the system organization and network load.

  8. Distributed systems architectures • Client-server architectures • Distributed services which are called on by clients. Servers that provide services are treated differently from clients that use services. • Distributed object architectures • No distinction between clients and servers. Any object on the system may provide and use services from other objects.

  9. Middleware • Software that manages and supports the different components of a distributed system. In essence, it sits in the middle of the system. • Middleware is usually off-the-shelf rather than specially written software. • Examples • Transaction processing monitors; • Data converters; • Communication controllers.

  10. Multiprocessor architectures • Simplest distributed system model. • System composed of multiple processes which may (but need not) execute on different processors. • Architectural model of many large real-time systems. • Distribution of process to processor may be pre-ordered or may be under the control of a dispatcher.

  11. A multiprocessor traffic control system

  12. Client-server architectures • The application is modeled as a set of services that are provided by servers and a set of clients that use these services. • Clients know of servers but servers need not know of clients. • Clients and servers are logical processes • The mapping of processors to processes is not necessarily 1 : 1.

  13. A client-server system

  14. Computers in a C/S network

  15. Application layers

  16. Thin and fat clients

  17. A client-server ATM system

  18. A 3-tier C/S architecture

  19. An internet banking system

  20. Distributed object architecture

  21. A data mining system

  22. CORBA application structure

  23. ORB-based object communications

  24. Inter-ORB communications

  25. Decentralized p2p architecture

  26. Semi-centralized p2p architecture

  27. Web services

  28. Automotive system

  29. Homework Names etc. on upper right, please • Required • By 11 Oct 2004 • For 20 points, answer in detail • 12.3, 12.8 (@10) [use computer-drawn diagrams for these two] • For 5 points, answer in detail 12.5 • Optional • By 18 Oct 2004 • For a maximum of 8 additional points, answer any or all of • 12.1, 12.2, 12.4, 12.6 (@2)

  30. DISCUSSION

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