chap18 - Chapter 18 Distributed Software Engineering...

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Chapter 18 Distributed Software Engineering Slide 1 Chapter 18 Distributed Software Engineering
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Chapter 18 Distributed Software Engineering Slide 2 Topics covered Distributed systems characteristics and issues Models of component interaction Client–server computing Architectural patterns for distributed systems Software as a service
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Chapter 18 Distributed Software Engineering Slide 3 Distributed systems Virtually all large computer-based systems are now distributed systems. Processing is distributed over several computers rather than confined to a single machine. Appears to the user as a single, coherent system.
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Chapter 18 Distributed Software Engineering Slide 4 Distributed system characteristics / advantages Resource sharing (hardware and software) Openness (standard protocols allow equipment and software from different vendors to be combined) Concurrency (parallel processing to enhance performance) Scalability (increased throughput by adding new resources up to capacity of network) Fault tolerance (potential to continue in operation after a fault has occurred)
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Chapter 18 Distributed Software Engineering Slide 5 Distributed systems issues Distributed systems are more complex than systems that run on a single processor. Complexity arises because different parts of the system are independently managed as is the network. There is no single authority in charge of the system so top-down control is impossible.
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Chapter 18 Distributed Software Engineering Slide 6 Design issues Transparency : To what extent should the distributed system appear to the user as a single system? Openness : Should a system be designed using standard protocols that support interoperability? Scalability : How can the system be constructed so that it is scalable? (cont’d)
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Chapter 18 Distributed Software Engineering Slide 7 Design issues (cont’d) Security : How can usable security policies be defined and implemented? Quality of service : How should the quality of service be specified. Failure management : How can system failures be detected, contained, and repaired?
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Chapter 18 Distributed Software Engineering Slide 8 Transparency Ideally, users should not be aware that a system is distributed and services should be independent of how they are distributed. In practice, this is impossible because parts of the system are independently managed and because of network delays. (It’s often better to make users aware of distribution so that they can cope with problems.) To achieve transparency, resources should be abstracted and addressed logically rather than physically. Middleware maps logical to physical resources.
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Chapter 18 Distributed Software Engineering Slide 9 Openness Open distributed systems are systems that are built according to generally accepted standards.
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This note was uploaded on 05/27/2011 for the course CEN 5035 taught by Professor Staff during the Fall '08 term at University of Florida.

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chap18 - Chapter 18 Distributed Software Engineering...

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