Lecture26

Lecture26 - ECE-547 Introduction to Computer Communication...

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Purdue University ECE ECE - - 547 547 Introduction to Computer Introduction to Computer Communication Networks Communication Networks Instructor: Instructor: Xiaojun Xiaojun Lin Lin Lecture 26 Lecture 26
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Purdue University Generalizing the Sliding Window Generalizing the Sliding Window Concept Concept ¾ Arrivals at V.C. are controlled depending on packets in V.C.: ¾ Arrival rate is now a function of the number in the queue: λ (n) ¾ Idea: if n is large (n) and vice versa.
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Purdue University ¾ Product form solution still exists. ¾ Want to find optimal control, i.e., find λ (n) such that γ is maximized subject to μE(T) L 12 3 M μ 1 μ 2 μ 3 μ M N (n)
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Purdue University Optimal Control Optimal Control ¾ Proof: A.A. Lazar “Optimal Flow Control of a Class of Queueing Networks”, in IEEE Transaction on Automatic Control, 1983. ¾ Best control is Sliding Window Control! if () 0 if cn N n nN λ = > ¾ Let (n) c ¾ Best control algorithm is of the form:
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Purdue University IBM SNA Virtual Route Pacing IBM SNA Virtual Route Pacing Protocol Protocol ¾ SNA: System Network Architecture ¾ Virtual Route Pacing Protocol: ¾ A fixed window of size k is initially established over a Virtual Route (VR) ¾ Pacing count PC = k . ¾ PC is decremented every time a packet enters a Virtual Route. ¾ Packets are withheld from entering network if PC = 0
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Purdue University Virtual Route Pacing Protocol: cont. Virtual Route Pacing Protocol: cont. ¾ First packet in a given window generates a special ACK called Virtual Route Pacing Response (VRPS) ¾ On arrival of VRPS at the source: PC=PC + k 0 <= PC <= 2k -1
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Purdue University Virtual Route Pacing Protocol: cont. Virtual Route Pacing Protocol: cont. 12 3 M μ 1 μ 2 μ 3 μ M 2k-1 λ SD ij PC -counter k-box
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Purdue University Comparison of all Three Schemes Comparison of all Three Schemes γ μE(T) Sliding Window SNA Fixed ACK at end
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Purdue University TCP/IP Architecture TCP/IP Architecture Application Transport Internet Network Interface Application Transport Internet Network Interface Internet Network Interface Network 1 Network 2 Machine A Machine B Router/Gateway
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Lecture26 - ECE-547 Introduction to Computer Communication...

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