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What does active queue management mean3/13/2024 The other type is the queue management algorithms, especially active queue management schemes, exemplified by Random Early Detection(RED), and recent Flow RED(FRED) and Stable RED(SRED).ġ9 Active Queue Manament With Enhancement to FairnessįIFO Approximate fair bandwidth allocation Provide isolation from unresponsive flows Be as simple as RED The goal of our work is to design a router method that can provide isolation from unresponsive flows similar to what FQ does, as well as be simple to implement as RED. And more recent algorithms like core stateless fair queueing and stocastic fair queueing. One is the scheduling algorithm, such as the well-known Fair queueing. There are generally two types of router algorithms associated with the congestion control. CHOKe, AFD, WRED To solve the problem mentioned above, routers adopt measures to isolate unresponsive flows and to provide Quality of Service to all users. FQ, CSFQ, SFQ queue management algorithms with fairness enhancement: e.g. UDP) provide Quality of Service to all users Two ways to do it scheduling algorithms: e.g. What routers want to do? isolate unresponsive flows (e.g. However, if the network is congested, unresponsive flows could take up all the scarce network bandwidth and starve out the adaptive flows. If the network is not congested, all these type of applications can coexist without affecting each other. Also there are badly implemented TCPs which don’t back off properly either. These types of traffic don’t back off as the TCP flows do. However, as the Internet grows, there are more and more packet radio and packet video applications running through the Internet. It depends on the transport layer protocol like TCP to provide good service under heavy load. Udp tcp tcp Connectionless Best-Effort The Internet The Internet protocol delivers connectionless, best-effort service. Lower buffer delay: good interactive service qavg is controlled to be small Given responsive flows: packet dropping is reduced early congestion indication allows traffic to throttle back before congestion Given responsive flows: fair bandwidth allocation Packets are randomly dropped Each flow has the same probability of being discardedġ5 Effectiveness of RED - Full-Queue & Bias against bursty trafficĭrop packets probabilistically in anticipation of congestion not when queue is full Use qavg to decide packet dropping probability: allow instantaneous bursts Solve tail-drop problems no lock-out behavior no full queue no bias against bursty flow no global synchronization Provide better QoS at network nodes low steady-state delay lower packet droppingĪrriving packet AvgQsize > Minth? no Admit the new packet yes AvgQsize > Maxth? no yes end Drop the new packet Admit packet with a probability p end endġ3 RED Dropping Curve 1 Drop Probability maxp minth maxthġ4 Effectiveness of RED - Lock-Out & Global Synchronization Only drop packets when queue is full long steady-state delayĩ Tail Drop Queue Management Global Synchronizationĭrop from front on full queue Drop at random on full queue both solve the lock-out problem both have the full-queues problem W/R C _ + q N + _ 0.5 - p Time Delay Queue Management + 1ĥ Drop Tail - problems Lock out Full queue Bias against bursty traffic sending rateĤ TCP+Queue Management - A closed-loop control system At the end of the talk, I will give a summary.ģ Queue Management: Drops/Marks - A Feedback Mechanism To Regulate End TCP HostsĮnd hosts send TCP traffic -> Queue size Network elements, switches/routers, generate drops/marks based on their queue sizes Drops/Marks: regulation messages to end hosts TCP sources respond to drops/marks by cutting down their windows, i.e. In the implementation section our proposal will be discussed. We also studied how to use the CHOKe algorithm in a real system. Analytical models were also developed to give us insights into CHOKe’s behavior. After introducing the CHOKe algorithm, the simulation result will be presented to show the performance of CHOKe. It is a randomized algorithm in which no state information needs to be maintained. The acronym will become clear once I explain how the scheme works. Then, I will introduce the choke algorithm. Pointing out what kind of the problem that we are trying to solve. First, I am going to give the background behind this work. This is a joint work by Konstantinos Psounis, myself and my advisor Balaji Prabhakar.Ģ Outline Queue Management Traditional Queue Managementĭrop as a way to feedback to TCP sources Part of a closed-loop Traditional Queue Management Drop Tail Problems Active Queue Management RED CHOKe AFD Here is the outline of my talk. Rong Pan Cisco System EE384y Spring Quarter 2008 Good afternoon, Today, I am going to talk about an active queue management scheme which aims to approximate fair bandwidth allocation. Presentation on theme: "Active Queue Management"- Presentation transcript:
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