交通控制-全文預(yù)覽
【正文】 eedback delay ?Low cell loss Feedback Mechanisms ?Transmission rate characteristics: ?Allowed cell rate ?Minimum cell rate ?Peak cell rate ?Initial cell rate ?Start with ACR=ICR ?Adjust ACR based on feedback from work ?Resource management cells ?Congestion indication bit ?No increase bit ?Explicit cell rate field Variations in Allowed Cell Rate Cell Flow Rate Control Feedback ?EFCI (Explicit forward congestion indication) marking ?Relative rate marking ?Explicit rate marking Frame Relay Congestion Control ?Minimize discards ?Miantain agreed QoS ?Minimize probability of one end user monoply ?Simple to implement ?Little overhead on work or user ?Create minimal additional traffic ?Distribute resources fairly ?Limit spread of congestion ?Operate effectively regardless of traffic flow ?Minimum impact on other systems ?Minimize variance in QoS Techniques ?Discard strategy ?Congestion avoidance ?Explicit signaling ?Congestion recovery ?Implicit signaling mechanism Traffic Rate Management ?Must discard frames to cope with congestion ?Arbitrarily, no regard for source ?No reward for restraint so end systems transmit as fast as possible ?Committed information rate (CIR) ?Data in excess of this liable to discard ?Not guaranteed ?Aggregate CIR should not exceed physical data rate ?Committed burst size ?Excess burst size Operation of CIR Relationship Among Congestion Parameters Explicit Signaling ?Network alerts end systems of growing congestion ?Backward explicit congestion notification ?Forward explicit congestion notification ?Frame handler monitors its queues ?May notify some or all logical connections ?User response ?Reduce rate 謝謝觀看 /歡迎下載 BY FAITH I MEAN A VISION OF GOOD ONE CHERISHES AND THE ENTHUSIASM THAT PUSHES ONE TO SEEK ITS FULFILLMENT REGARDLESS OF OBSTACLES. BY FAITH I BY FAITH 。ρ=2MB/s Host: ρ=25MB/s。交通控制 ?流量控制 (flow) ?調(diào)節(jié)傳輸速率 ?端對端、節(jié)點對節(jié)點 ?擁擠（擁塞 congestion） 控制 ?保持網(wǎng)絡(luò)分組數(shù)目不超過某一限度，一旦越過這一界限，性能顯著下降。 Mechanisms for Congestion Control 隱式 顯式 Backpressure： 反壓 ?If node bees congested it can slow down or halt flow of packets from other nodes ?May mean that other nodes have to apply control on ining packet rates ?Propagates back to source ?Can restrict to lo
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