A Review of Router based Congestion Control Algorithms <s> VI. DISCUSSION <s> The authors present random early detection (RED) gateways for congestion avoidance in packet-switched networks. The gateway detects incipient congestion by computing the average queue size. The gateway could notify connections of congestion either by dropping packets arriving at the gateway or by setting a bit in packet headers. When the average queue size exceeds a present threshold, the gateway drops or marks each arriving packet with a certain probability, where the exact probability is a function of the average queue size. RED gateways keep the average queue size low while allowing occasional bursts of packets in the queue. During congestion, the probability that the gateway notifies a particular connection to reduce its window is roughly proportional to that connection's share of the bandwidth through the gateway. RED gateways are designed to accompany a transport-layer congestion control protocol such as TCP. The RED gateway has no bias against bursty traffic and avoids the global synchronization of many connections decreasing their window at the same time. Simulations of a TCP/IP network are used to illustrate the performance of RED gateways. > <s> BIB001 </s> A Review of Router based Congestion Control Algorithms <s> VI. DISCUSSION <s> We investigate the problem of providing a fair bandwidth allocation to each of n flows that share the outgoing link of a congested router. The buffer at the outgoing link is a simple FIFO, shared by packets belonging to the n flows. We devise a simple packet dropping scheme, called CHOKe, that discriminates against the flows which submit more packets per second than is allowed by their fair share. By doing this, the scheme aims to approximate the fair queueing policy. Since it is stateless and easy to implement, CHOKe controls unresponsive or misbehaving flows with a minimum overhead. <s> BIB002 </s> A Review of Router based Congestion Control Algorithms <s> VI. DISCUSSION <s> Abstract This paper describes the Dynamic-RED (DRED) algorithm, an active queue management algorithm for TCP/IP networks. In random early detection (RED), one of the goals is to stabilize the queue lengths in routers. However, the current version of RED does not succeed in this goal because the equilibrium queue length strongly depends on the number of active TCP connections. Using a simple control-theoretic approach, DRED randomly discards packets with a load-dependent probability when a buffer in a router gets congested. Over a wide range of load levels, DRED is able to stabilize a router queue occupancy at a level independent of the number of active TCP connections. The algorithm achieves this without estimating the number of active TCP connections or flows and without collecting or analyzing state information on individual flows. The benefits of stabilized queues in a network are high resources utilization, bounded delays, more certain buffer provisioning, and traffic-load-independent network performance in terms of traffic intensity and number of connections. <s> BIB003 </s> A Review of Router based Congestion Control Algorithms <s> VI. DISCUSSION <s> This paper describes and evaluates stochastic fair blue (SFB), a novel technique for enforcing fairness among a large number of rows. SFB scalably detects and rate-limits non-responsive flows through the use of a marking probability derived from the blue queue management algorithm and a Bloom (1970) filter. Using analysis and simulation, SFB is shown to effectively handle non-responsive flows using an extremely small amount of state information. <s> BIB004 </s> A Review of Router based Congestion Control Algorithms <s> VI. DISCUSSION <s> Virtual Queue-based marking schemes have been recently proposed for AQM (Active Queue Management) in Internet routers. We consider a particular scheme, which we call the Adaptive Virtual Queue (AVQ), and study its following properties: stability in the presence of feedback delays, its ability to maintain small queue lengths and its robustness in the presence of extremely short flows (the so-called web mice). Using a mathematical tool motivated by the earlier work of Hollot et al, we present a simple rule to design the parameters of the AVQ algorithm. We then compare its performance through simulation with several well-known AQM schemes such as RED, REM, PI controller and a non-adaptive virtual queue algorithm. With a view towards implementation, we show that AVQ can be implemented as a simple token bucket using only a few lines of code. <s> BIB005 </s> A Review of Router based Congestion Control Algorithms <s> VI. DISCUSSION <s> In this paper, we propose a new AQM algorithm that considers both the average queue length and the estimated packet arrival rate together in order to detect and control incipient congestion. It predicts the average queue length and controls it to maintain a certain reference value to achieve high link utilization and low queueing delay. Simulation results confirm the stability of our proposed algorithm under various network environments and show its performance advantages over other competitive AQM algorithms <s> BIB006 </s> A Review of Router based Congestion Control Algorithms <s> VI. DISCUSSION <s> We focus on the problem of the stability of congestion control for networks with large round-trip communication delays. Nearly all the existing AQM schemes neglect the impact large communication delay has on system behavior, such as stability, robustness and convergence. The drastic queue oscillations in large delay networks of PI, REM and DC-AQM decrease link utilization and introduce avoidable delay jitter. To address this problem, we propose a robust IMC-PID congestion controller based on the internal model control principle to restrict the negative impact of the stability caused by large delay. Simulation results demonstrate that the integrated performance of our proposed scheme outperforms others as communication delay increases, and achieves high link utilization and small delay jitter. <s> BIB007 </s> A Review of Router based Congestion Control Algorithms <s> VI. DISCUSSION <s> A robust active queue management (AQM) scheme based on H-infinity theory is presented for the problem of congestion control in TCP communication networks. In TCP/IP networks, the packet-dropping probability function is considered as a control input, and network parameters are time-varying. Thus a TCP/AQM controller is modeled as a uncertain time-delay system with a saturated input. The corresponding existence condition of the observer and controller are obtained by applying Lyapunov-Krasovskii function approach and the linear matrix inequality technique. Simulation results show that the proposed scheme can track the desired queue length very quickly under various network conditions, and avoid the problem of dynamic network congestion. <s> BIB008 </s> A Review of Router based Congestion Control Algorithms <s> VI. DISCUSSION <s> Since its formal introduction to IP networks in 1993 as a viable complementary approach for congestion control, there has been a steady stream of research output with respect to Active Queue Management (AQM). This survey attempts to travel the trajectory of AQM research from 1993 with the first algorithm, Random Early Detection (RED), to current work in 2011. In this survey we discuss the general attributes of AQM schemes, and the design approaches taken such as heuristic, control-theoretic and deterministic optimization. Of interest is the role of AQM in QoS provisioning particularly in the DiffServ context, as well as the role of AQM in the wireless domain. For each section, example algorithms from the research literature are presented. <s> BIB009
This section we discuss the significance of router based approach while congestion control. We also summarize the various possible classifications of these approaches, their relative merits and demerits. Hong et al BIB006 (2007) commented that TCP congestion control alone is less effective while controlling congestion. Floyd et al BIB001 (1993) first proposed a router based method for congestionavoidance and emphasized that most effective congestion detection can occur at the router level in cooperation with source level methods. Pan et al BIB002 (2000) considered aggressive nature of non-TCP (unresponsive) applications as a cause of congestion collapse. Therefore it is required to have router level mechanism to prevent TCP (responsive) flows from aggressiveness of nonresponsive flows. Aweya et al BIB003 (2001) commented that buffer overflow is a major issue while using TCP based congestion control with drop-tail routers and for avoiding these overflows router should use some active queue management scheme. Feng et al BIB004 (2001) considered nonresponsive flow's aggressiveness as a dangerous situation for TCP flows as it causes congestion collapse. Chang et al  (2006) considered network congestion a severe problem as it leads wastage of network resources due to queue overflow at router.Wang et al BIB007 (2008) commented that Congestion control in communication networks has become increasingly important due to the explosive expansion and the growth of traffic. From the control theory point of view, congestion control problems are complex and challenging due to their highdimensional, nonlinear, and dynamic properties. Jing et al BIB008 (2008) considered congestion control a major problem because it severely affects quality of service of the network. Therefore it is not reasonable to rely only on end host forcongestion control; some source level as well as router  . Therefore different academicians and practitioners had proposed two approaches for congestion control. First one is 'source based' approach which works as end to end protocol implemented in TCP. Second one is 'router based' approach also known as 'active queue management' schemes implemented in Router. Router based congestion control methods are proactive in nature. Router continuously measure the traffic load and if there is any symptoms of traffic overload which causes congestion , it sends a signal to source host to slow down its transmission speed before congestion occurs. Router based methods sends incipient congestion signal by marking packets with a mark probability. Based on the mark probability calculation criteria router based methods are categorized as: Queue length based, Rate based and Hybrid approach. Based on the nature of solution router based approach are classified as: Heuristic approach, Optimization approach and Control Theoretic approach BIB009 . 1) Heuristic Approach Heuristic approach was followed by earlier router based methods like RED proposed by Floyd et al BIB001 (1993). RED detects incipient congestion by computing the average queue size and control the average queue size before the gateway queue overflows. They considered it an effective mechanism for congestion avoidance at the gateway; in cooperation with network transport protocols because it is unbiased against bursty traffic and avoid global synchronization. Pan et al BIB002 (2000) stated that earlier methods for congestion control are either easy to implement or able to achieve flow fairness, but not both simultaneously and they proposed an active queue management method, called CHOKe (CHOose and Keep for responsive flows, Choose and Kill for unresponsive flows) that is simple to implement (since it is stateless) and provide fairness by differentially penalizing misbehaving flows by dropping more of their packets. Kunniyur et al BIB005 (2001) have given a virtual queue based AQM method AVQ (Adaptive Virtual Queue) which uses a rate based marking approach and it can achieve low loss with high link utilization, more robust to the presence of extremely short flow or variability in the number of long flow in the network. Feng et al BIB004 (2001) proposed SFB which scalably detects and rate-limits nonresponsive flows through the use of a marking probability derived from the BLUE queue management algorithm and a Bloom filter. Chan et al [31] (2003) found that most of the existing AQM schemes cannot provide accurate fair bandwidth sharing while being scalable because of per flow state management. They proposed a novel AQM scheme, called CApture-Recapture (CARE) which requires small bounded number of states but can provide fair bandwidth sharing similar to those that can be provided with per flow mechanisms. Thus CARE can simultaneously achieve high quality-of-service (QoS), high scalability, and robustness which are necessary for high speed implementation.