l15_march5 - Lecture 15 Internet resource allocation and...

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1 Lecture 15 Internet resource allocation and QoS Resource Reservation Protocol Integrated Services Differentiated Services
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2 QoS in a datagram network ? Packet Classification. Buffer acceptance algorithms. Explicit Congestion Notification. Flow measurements
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3 A QoS Capable Router Shaper Policer Classifier Output link Input flows Dispatcher and Buffer Acceptance
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4 Packet classification Identify the flow the packet belongs to. The edge routers may be able to do that. MPLS – multi protocol label switch. Add an extra header in front of the IP header. Now a router decides the output link based upon the input link and the MPLS header.
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5 Buffer acceptance algorithms Tail Drop. RED – Random Early Detection RIO – Random Early Detection with In and Out packet dropping strategies.
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6 1.0 maxDropProb minThr_out maxThr_out minThr_in maxThr_in avgQue minThr_in maxThr_in sampleQueueLength dropProb low load maxThr_out minThr_out low load medium load medium load high load high load out in (a) (b) sampleQueueLength in out
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7 Explicit Congestion Notification (ECN) Routers could prevent congestion by informing the source of the packets when they become lightly congested, but before they start dropping packets. This strategy is called source quench .
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8 Source quench A router sets a congestion notification flag in the IP header to inform the destination that signs of congestion are visible.
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l15_march5 - Lecture 15 Internet resource allocation and...

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