cs6235-5B-net-sched

cs6235-5B-net-sched - CS 6235 9/27/2010 Network Scheduling...

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CS 6235 9/27/2010 Network Scheduling 1 1 CS4220 Embedded Systems CS6235 Real CS6235 Real-Time Systems Time Systems 5B: Network Scheduling Instructor: Calton Pu calton.pu@cc TAs: Qinyi Wu (qxw@cc) Peter Budny (peterb@cc) 2 OSI Reference Model Application Presentation Session Transport Network Data Link Physical board software Logical Link Control Media Access Control
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CS 6235 9/27/2010 Network Scheduling 2 3 Transmission Time Cost Above Cost of Interest (MAC) Cost Below Propagation Cost Below Cost of Interest (MAC) Cost Above Sender Receiver 4 Message Classification Synchronous messages Periodic, predictable stream (sensor data) Arrival time: job creation Length: job resource requirement Deadline: job completion requirement Asynchronous messages Aperiodic task communications, alerts Unpredictable arrivals, length, deadline
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CS 6235 9/27/2010 Network Scheduling 3 5 Access Arbitration Network as a shared resource Rate monotonic scheduling of bandwidth Desirable properties Bandwidth utilization (for synchronous) Robustness: not brittle Timing fault isolation and limitation Accommodate asynchronous messages Low run-time overhead 6 Rate Monotonic Scheduler Classic hard real-time CPU scheduler Decides who gets the resource next CPU in the original work Network bandwidth in MAC Static scheduler: fixed priorities No dynamic priority adjustments Not a static schedule
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CS 6235 9/27/2010 Network Scheduling 4 7 RM Scheduling Algorithm Assumptions Jobs are periodic, marked by start and end Jobs are independent Shorter period jobs get higher priority Time line 8 RM for Networking Synchronous messages Arrival, length, deadline Time line
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CS 6235 9/27/2010 Network Scheduling 5 9
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cs6235-5B-net-sched - CS 6235 9/27/2010 Network Scheduling...

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