Lecture12nFull - COT 4600 Operating Systems Spring 2011...

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Click to edit Master subtitle style 8/1/11 Lecture 12 COT 4600 Operating Systems Spring 2011 Dan C. Marinescu Office: HEC 304 Office hours: Tu-Th 5:00 – 6:00 PM
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Lecture 12 8/1/11 n Last time: ¨ Client-server organization ¨ Intermediaries; Trusted Intermediaries; Thin clients ¨ Issues § Heterogeneity; little-endian and big-endian representation § Timing, response time. ¨ Examples: Event service, X11; Trusted intermediaries: Email, File Systems, Web Today ¨ Today ¨ Peer-to-peer systems ¨ Remote Procedure Call ¨ Strategies for name resolution ¨ Case study: DNS – Domain Name Service ¨ Case study: NFS – Network File System ¨ Next time n Virtualization Lecture 12 – Tuesday, February 22, 2011 22
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Lecture 12 8/1/11 33 3 Peer-to-peer systems n Decentralized architecture without a trusted intermediary. n Peers are both suppliers and consumers of resources, in contrast to the traditional client-server model where servers supply, and clients consume. n Peer-to-peer systems often implement an Application Layer overlay network on top of the native or physical network topology. Such overlays are used for indexing and peer discovery. n Content is typically exchanged directly over the underlying IP network. n Anonymous peer-to-peer systems implement extra routing layers to obscure the identity of the source or destination of queries. n In structured peer-to-peer networks, connections in the overlay are fixed. They typically use distributed hash table-based (DHT) indexing, such as in the Chord system developed at MIT n Unstructured peer-to-peer networks do not provide any algorithm for organization or optimization of network connections. n Advantagesl ¨ use of spare resources at many sites ¨ difficult to censor content n Disadvantage ¨ Finding information in a large peer-to-peer network is hard.
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Lecture 12 8/1/11 44 4 Remote procedure call (RPC) n Support inter-process communication of remotely located processes and allows implementation of client-server systems (RFC 1831) n Preserve the semantics of a local procedure call. n To use an RPC a process may use a special service: PORTMAP or RPCBIND available at port 111. A new RPC service uses the portmapper to register. The portmapper also allows a service lookup. n If the process knows the port number of the RPC it may call directly. n RPC/TCP and also RPC/UDP n Messages ¨ must be well-structured; contain the identification of the specific RPC ¨ are addressed to an RPC demon listening at an RPC port. n A machine independent representation of data & external data representation standard (XDR).
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Lecture 12 8/1/11 55 5 Stub n Unburdens a user from implementation details of the RPC; it hides: ¨ the marshalling of the arguments ¨ the communication details n The client calls the client stub which: 1. marshals the arguments of the call into messages 2. sends the message 3. waits for the responds 4. when the response arrives it un-marshals the results 5. returns to the client
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Lecture 12 8/1/11 66 6
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This note was uploaded on 07/30/2011 for the course COP 4600 taught by Professor Montagne during the Spring '08 term at University of Central Florida.

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Lecture12nFull - COT 4600 Operating Systems Spring 2011...

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