Computer Science 425 Distributed Systems CS 425 / CSE 424 / ECE 428Our Only Goal TodayCan you name some examples of Operating Systems?Slide 4What is an Operating System?Slide 6FOLDOC definitionCan you name some examples of Distributed Systems?Slide 9What is a Distributed System?Slide 11Textbook definitionsUnsatisfactorySlide 14Slide 15Slide 16A working definition for usA range of interesting problems for Distributed System designersDistributed Systems Design GoalsDistributed System Example -- the InternetThe InternetA Typical IntranetIntranetsInternet Apps: Their Protocols and Transport ProtocolsWWW: the HTTP ProtocolThe HTTP Protocol: MoreHTTP ExampleHTTP Example (cont.)Trying Out HTTP (Client Side) for YourselfDoes our Working Definition work for the http Web?“Important” Distributed Systems Issues“Important” Issues“Concepts”?How will you Learn?On the TextbookWhat assistance is available to you?If you’re still thinking, “Everything you’ve said so far is so boring...”…You can meet us anytimeReadingsHave a Good Weekend! 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-1Lecture 1-1Computer Science 425Distributed SystemsCS 425 / CSE 424 / ECE 428Computer Science 425Distributed SystemsCS 425 / CSE 424 / ECE 428Indranil Gupta (Indy)August 23, 2007 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-2Lecture 1-2Our Only Goal TodayOur Only Goal TodayTo Define the Term Distributed System 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-3Lecture 1-3Can you name some examples of Operating Systems?Can you name some examples of Operating Systems? 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-4Lecture 1-4Can you name some examples of Operating Systems?Can you name some examples of Operating Systems?…Linux WinXP Unix FreeBSD Mac2K Aegis Scout Hydra Mach SPINOS/2 Express Flux Hope SpringAntaresOS EOS LOS SQOS LittleOS TINOSPalmOS WinCE TinyOS… 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-5Lecture 1-5What is an Operating System?What is an Operating System? 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-6Lecture 1-6What is an Operating System?What is an Operating System?•User interface to hardware (device driver)•Provides abstractions (processes, file system)•Resource manager (scheduler)•Means of communication (networking)•… 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-7Lecture 1-7FOLDOC definitionFOLDOC definition•The low-level software which handles the interface to peripheral hardware, schedules tasks, allocates storage, and presents a default interface to the user when no application program is running.•The OS may be split into a kernel which is always present and various system programs which use facilities provided by the kernel to perform higher-level house-keeping tasks, often acting as servers in a client-server relationship.•Some would include a graphical user interface and window system as part of the OS, others would not. The operating system loader, BIOS, or other firmware required at boot time or when installing the operating system would generally not be considered part of the operating system, though this distinction is unclear in the case of a roamable operating system such as RISC OS.•The facilities an operating system provides and its general design philosophy exert an extremely strong influence on programming style and on the technical cultures that grow up around the machines on which it runs.(FOLDOC = Free On-Line Dictionary of Computing) 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-8Lecture 1-8Can you name some examples of Distributed Systems?Can you name some examples of Distributed Systems? 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-9Lecture 1-9Can you name some examples of Distributed Systems?Can you name some examples of Distributed Systems?•Client-Server •The Web•The Internet•An ad-hoc network•A sensor network•DNS•Kazaa (peer to peer overlays)•(The Solar System?)•(Society?)•(Food Chain?) 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-10Lecture 1-10What is a Distributed System?What is a Distributed System? 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-11Lecture 1-11FOLDOC definitionFOLDOC definitionA collection of (probably heterogeneous) automata whose distribution is transparent to the user so that the system appears as one local machine. This is in contrast to a network, where the user is aware that there are several machines, and their location, storage replication, load balancing and functionality is not transparent. Distributed systems usually use some kind of client-server organization. 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-12Lecture 1-12Textbook definitionsTextbook definitions•A distributed system is a collection of independent computers that appear to the users of the system as a single computer [Andrew Tanenbaum] •A distributed system is several computers doing something together. Thus, a distributed system has three primary characteristics: multiple computers, interconnections, and shared state[Michael Schroeder] 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-13Lecture 1-13UnsatisfactoryUnsatisfactory•Why are these definitions short? •Why do these definitions look inadequate to us?•Because we are interested in the insides of a distributed system–design and implementation–maintenance–study–Algorithmics (“protocols”) 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-14Lecture 1-14“I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description; and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that.”[Potter Stewart, Associate Justice, US Supreme Court (talking about his interpretation of a technical term laid down in the law, case Jacobellis versus Ohio 1964) ] 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-15Lecture 1-15(A) Plants and Animals interacting in the Food ChainWhich is a Distributed System – (A) or (B) ?Which is a Distributed System – (A) or (B) ?(A) 2002, M. T. Harandi and J. Hou (modified: I. Gupta) Lecture 1-16Lecture 1-16(B) The Internet (Internet Mapping Project, color coded by ISPs)(B) 2002, M. T.
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