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hw1 - a Explain how exactly once semantics can be achieved...

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CSCI 5105: Foundations of Modern Operating Systems Homework 1 Due: 02/15/2010 Maximum Marks: 50 Q1) What are some of the issues with deploying (or trying to deploy) RPC in heterogeneous  environments? (Not just in terms of Operating System heterogeneity). Q2) An RPC request is said to have at-least-once semantics if, once the request returns to the calling  application, it is guaranteed that the remote procedure was executed at least once on the server. This  makes sense for idempotent procedures. The other extreme is “at-most-once” semantics, where the  remote procedure is guaranteed not to be executed more than once. This makes sense for a non- idempotent procedure (though one certainly hopes that most of the time it is in fact executed once). Of  course, what we really want is “exactly once” semantics: a guarantee that the remote procedure is  executed exactly one time.
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Unformatted text preview: a. Explain how exactly once semantics can be achieved if we can guarantee that the server never crashes. b. Is exactly once semantics possible if we no longer have the no-crash guarantee? What additional mechanisms would be needed? Explain. Q3) When searching for files in an unstructured peer-to-peer system, it may help to restrict the search to nodes that have similar files as yourself. Explain how gossiping can help to find those nodes. Q4) Not every node in a peer-to-peer network should become a superpeer. What requirements should a node meet to be assigned as a superpeer? Explain based on the roles a superpeer is expected to play. Q5) A bottleneck in the BitTorrent architecture is the use of a single tracker per shared file. Describe how this can be made de-centralized and how it affects the rest of the architecture....
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