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Learn about the fundamentals of distributed systems, including their definition, examples, major challenges, and key aspects such as heterogeneity, openness, security, scalability, failure handling, concurrency, transparency, and mobility. Explore how the Internet, intranets, mobile computing, and client/server architectures are part of distributed systems.
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Distributed Systems Bina Ramamurthy From the CDK text
Introduction • Distributed system is the one in which hardware and software components at networked computers communicate and coordinate their activity only by passing messages. • Examples: Internet, intranet and mobile computing systems. From the CDK text
Major Challenges • Heterogeneity of components • Openness • interfacing and • addition and removal of components • Security • Scalability : ability to work well when number of users increases • Failure handling • Concurrency • Transparency From the CDK text
Internet • Internet is a very large distributed system. • Interconnection of a collection of heterogeneous networks of computers. • Services: world wide web (www), file transfers (ftp), email, etc. From the CDK text
intranet % % ISP % % backbone satellite link desktop computer: server: network link: A typical portion of the Internet From the CDK text
A typical intranet From the CDK text
Mobile and Ubiquitous computing • Technological advances in device miniaturization and wireless networking have led to integration of small and portable devices into distributed systems. • Laptop computers, hand held devices, wearable devices, appliances such as washing machines and refrigerators. • What are some of the issues here? From the CDK text
Portable and handheld devices in a distributed system From the CDK text
Client/Server • Server: refers to a process on a networked computer that accepts requests from other (local or remote) processes to perform a service and responds appropriately. • Client: requesting process in the above is referred to as the client. • Request and response are in the form of messages. • Client is said to invoke an operation on the server. • Many distributed systems today are constructed out of interacting clients/servers. From the CDK text
http://www.google.comlsearch?q=kindberg www.google.com Browsers Web servers Internet www.cdk3.net http://www.cdk3.net/ www.w3c.org http://www.w3c.org/Protocols/Activity.html File system of Protocols www.w3c.org Activity.html Web servers and web browsers Reading assignment: Section 1.3.1 From the CDK text
Date Web servers Computers 188 0 1979, Dec. 1989, July 130,000 0 1999, July 56,218,000 5,560,866 Computers in the Internet From the CDK text
Transparencies • Access transparency: enables local and remote resources to be accessed using identical operations. • Location transparency: enables resources to be accessed without knowledge of their location. • Concurrency transparency: enables several processes to operate concurrently using shared resources without interference between them. • Replication transparency: enables multiple instances of resources to be used to increase reliability and performance without knowledge of the replicas by users or application programmers. • Failure transparency: enables the concealment of faults, allowing users and application programs to complete their tasks despite the failure of hardware or software components. • Mobility transparency: allows the movement of resources and clients within a system without affecting the operation of users or programs. • Performance transparency: allows the system to be reconfigured to improve performance as loads vary. • Performance transparency: allows the system and applications to expand in scale without change to the system structure or the application algorithms. From the CDK text