Processes - Class notes on Synchronous and Asynchronous...

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Unformatted text preview: Class notes on Synchronous and Asynchronous Communication, Process Models and Monitoring Models Dan C. Marinescu April 15, 2009 Contents 1 Synchronous and Asynchronous Message Passing System Models 1 1.1 Time and the Process Channel Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Synchronous Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3 Asynchronous Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.4 Final Remarks on Synchronous and Asynchronous Systems . . . . . . . . . . . . . . . . . . . 7 2 Process Models 7 2.1 Processes and Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2 Local and Global States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.3 Process Coordination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.4 Time, Time Intervals, and Global Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.5 Cause-Effect Relationship, Concurrent Events . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.6 Logical Clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.7 Message Delivery to Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.8 Process Algebra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.9 Final Remarks on Process Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3 Monitoring Models 16 3.1 Runs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.2 Cuts; the Frontier of a Cut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3 Consistent Cuts and Runs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.4 Causal History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.5 Consistent Global States and Distributed Snapshots . . . . . . . . . . . . . . . . . . . . . . . 18 3.6 Monitoring and Intrusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 1 Synchronous and Asynchronous Message Passing System Models 1.1 Time and the Process Channel Model Given a group of n processes, G = ( p 1 ,p 2 ,...,p n ) , communicating by means of messages, each process must be able to decide if the lack of a response from another process is due to: (i) the failure of the remote process, (ii) the failure of the communication channel, or (iii) there is no failure, but either the remote process or the communication channel are slow, and the response will eventually be delivered....
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Processes - Class notes on Synchronous and Asynchronous...

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