Lecture24_2up - ECE-547 Introduction to Computer...

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1 Purdue University ECE ECE -547 547 Introduction to Computer Introduction to Computer Communication Networks Communication Networks Instructor: Instructor: Xiaojun Xiaojun Lin Lin Lecture 24 Lecture 24 Purdue University Model for Flow Control Model for Flow Control ¾ Assumptions: ¾ Infinite buffers ¾ Zero propagation delay ¾ Zero acknowledgement delay ¾ Poisson arrivals and exponential service times ¾ Operations: ¾ Packets that arrive into the network & find N packets in the V.C. are dropped.
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2 Purdue University Closed Closed Queueing Queueing Model Model ¾ V.C. with Poisson arrivals ( λ ). ¾ Service time at each queue i is exponentially distributed i ). ¾ No ack. delay or propagation delay. 12 3 M μ 1 μ 2 μ 3 μ M N Purdue University Closed Closed Queueing Queueing Model Model ¾ Question we would like to answer: ¾ Time Delay ¾ Throughput in the V.C. using a sliding window flow control mechanism ¾ Qualitative feel: ¾ No Control: λ Delay Throughput ¾ Control: •(1) λ Delay Throughput (bounded by N) •(2) N Delay Throughput
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3 Purdue University Sliding Window Flow Control Sliding Window Flow Control ¾ Best Control Scheme: ¾ Shortest delay for a given throughput, or vice- versa. ¾ No propagation delay: ¾ Optimum N M Purdue University Quantitative Analysis Quantitative Analysis ¾ Fact: ¾ For product-form queueing networks, any subnetwork can be replaced by one or more “composite queues” with a state dependent service rate ¾ Remaining network retains exactly the same statistical behavior.
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This note was uploaded on 01/06/2010 for the course ECE 547 taught by Professor Xiaojunlin during the Spring '09 term at Purdue University-West Lafayette.

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Lecture24_2up - ECE-547 Introduction to Computer...

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