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computer networks

This tag is associated with 8 posts

Reliable one-to-one Communication

By ⋅ January 25, 2011 ⋅ Post a comment

Although this is stated in the post about distributed system models, I better write it down again. Validity: Any message sent to the outgoing buffer is eventually delivered in the incoming buffer Integrity: Received messages are identical to the ones sent and delivered just once

Replication in Distributed Systems

By ⋅ January 19, 2011 ⋅ Post a comment

System Model Assume synchronous system with crashing the only fail Replica Managers contain the replica in a computer and perform operations upon them Front-end issues request to one or more replica managers Coordination: Replica managers coordinate the requests FIFO, Casual, Total Replica manager pass back the first result for responsiveness or what majority has reply [...]

Coordination and Agreement in Distributed Systems

By ⋅ January 18, 2011 ⋅ Post a comment

For the rest of the post we assume the following: Processes connected by reliable channels Only possible file is a crash Systems Asynchronous Distributed Mutual Exclusion If server involved allowing access to one process at a time Algorithms evaluated following: Bandwidth consumed Client delay Throughput of the system Central Server Algorithm: A process sends a [...]

Time and Global States in Distributed Systems

By ⋅ January 17, 2011 ⋅ Post a comment

Simple Synchronization in Synchronous Systems A process sends its internal clock to a UTC Server t + Ttrans not valid because of network variations instead uses t + (max +min) / 2, being transmission max/min bounds Cristian’s Algorithm Method achieves synchronization if round-trip is sufficiently short compared with the accuracy P1 ask for time to P2 P1 receives [...]

Name Services in Distributed Systems

By ⋅ January 16, 2011 ⋅ Post a comment

Names are not the only useful means, descriptive attributes can be used too. A client knowing just a few characteristics needs to be able to find a proper service provider. Pure Names: uninterpreted bit patterns, always need to be lookup. e.g. Object’s address Non-Pure Names: contain information about the location Binding: Association between name and [...]

Distributed File Systems

By ⋅ January 15, 2011 ⋅ Post a comment

Requirements of a Distributed File System Transparency: Access Transparency: Programs written to operate local files are able to access remote ones without modification Location Transparency: Uniform name space, files maybe relocated without changing path-names Mobility Transparency: no change of administration tables or client programs when files are moved Performance Transparency: Clients continue to perform satisfactorily [...]

Distributed Objects and Remote Invocation

By ⋅ January 14, 2011 ⋅ Post a comment

Properties of middle providing remote invocation and events: Location transparency:  Invoking client does know where the receiver is located nor even those objects sending or receiving events. Communication Protocols: UDP/TCP Computer Hardware: They hide properties such byte-ordering Operating Systems: Independent from OSs Programming Languages:  CORBA allows interaction between different programming languages Distributed Objects Can be [...]

Group Communication in Distributed Systems

By ⋅ January 13, 2011 ⋅ Post a comment

Charateristics: Fault tolerance based on replicated services: Client request multicast to a bunch of server. Finding the discovery servers in spontaneous networking Better performance through replicated data: when a value changes it is multicasted Propagation of event notifications: IP Multicast: Sender is unaware of the identities of the recipients Multicast group is a class D [...]

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