A Review of Router based Congestion Control Algorithms <s> IV. SIGNIFICANCE OF ROUTER BASED CONGESTION CONTROL <s> We propose a new active queue management algorithm, called average rate early detection (ARED). An ARED gateway measures/uses the average packet enqueue rate as a congestion indicator, and judiciously signals end hosts of incipient congestion, with the objective of reducing packet loss ratio and improving link utilization. We show (via simulation in ns-2) that the performance of ARED is better than that of RED and comparable to that of BLUE in terms of packet loss rate and link utilization. We also explore the use of ARED in the context of the differentiated services architecture. We show analytically that the widely referenced queue management mechanism, RED with in and out (RIO) cannot achieve throughput assurance and proportional bandwidth sharing. We then extend ARED and propose a new queue management mechanism, called ARED with in and out (AIO), in the assured services architecture. To share surplus bandwidth in a rate-proportional manner, we incorporate into AIO the derived analytic results, and propose an enhanced version of AIO, called the differentiated-rate AIO (DAIO) mechanism. <s> BIB001 </s> A Review of Router based Congestion Control Algorithms <s> IV. SIGNIFICANCE OF ROUTER BASED CONGESTION CONTROL <s> In active queue management (AQM), core routers signal transmission control protocol (TCP) sources with the objective of managing queue utilization and delay. It is essentially a feedback control problem. Based on a recently developed dynamic model of TCP congestion-avoidance mode, this paper does three things: 1) it relates key network parameters such as the number of TCP sessions, link capacity and round-trip time to the underlying feedback control problem; 2) it analyzes the present de facto AQM standard: random early detection (RED) and determines that REDs queue-averaging is not beneficial; and 3) it recommends alternative AQM schemes which amount to classical proportional and proportional-integral control. We illustrate our results using ns simulations and demonstrate the practical impact of proportional-integral control on managing queue utilization and delay. <s> BIB002 </s> A Review of Router based Congestion Control Algorithms <s> IV. SIGNIFICANCE OF ROUTER BASED CONGESTION CONTROL <s> This paper is aimed at designing a congestion control system that scales gracefully with network capacity, providing high utilization, low queueing delay, dynamic stability, and fairness among users. The focus is on developing decentralized control laws at end-systems and routers at the level of fluid-flow models, that can provably satisfy such properties in arbitrary networks, and subsequently approximate these features through practical packet-level implementations. Two families of control laws are developed. The first "dual" control law is able to achieve the first three objectives for arbitrary networks and delays, but is forced to constrain the resource allocation policy. We subsequently develop a "primal-dual" law that overcomes this limitation and allows sources to match their steady-state preferences at a slower time-scale, provided a bound on round-trip-times is known. We develop two packet-level implementations of this protocol, using 1) ECN marking, and 2) queueing delay, as means of communicating the congestion measure from links to sources. We demonstrate using ns-2 simulations the stability of the protocol and its equilibrium features in terms of utilization, queueing and fairness, under a variety of scaling parameters. <s> BIB003 </s> A Review of Router based Congestion Control Algorithms <s> IV. SIGNIFICANCE OF ROUTER BASED CONGESTION CONTROL <s> In the recent years, several transport protocols have been proposed for very high bandwidth-delay product networks. However, little is known about the performance of these new mechanisms as well as the interaction with other elements of the network (such as the RED queue management). On the other hand, the control-theoretic approach has proved to be a very useful tool in order to get analytical insight into the performance of congestion control algorithms. In this paper, a control-theoretic research framework is designed and implemented for analyzing high speed transport protocol proposals in network environments with RED active queue management. As a case study, a comprehensive control-theoretic analysis of a promising proposal, namely the HighSpeed TCP is provided. The main contributions of this paper are the following. First, we provide a fluid-flow model for HighSpeed TCP/RED networks. Second, a comprehensive and systematic implementation methodology is described in detail, and a Simulink-based framework is designed for analyzing fluid-based models. Third, we derive a stability condition for HighSpeed TCP/RED networks. The flow-level results are validated by packet-level simulations conducted in Ns-2. Finally, an extension of the framework is presented that makes it capable of describing the interaction of different transport protocols. <s> BIB004 </s> A Review of Router based Congestion Control Algorithms <s> IV. SIGNIFICANCE OF ROUTER BASED CONGESTION CONTROL <s> Several variants of the Transmission Control Protocol (TCP) have been proposed for overcoming the inefficiency of the TCP Reno when operating in high-speed networks. However, these variants by themselves cannot prevent network congestion. Congestion avoidance also relies on other mechanisms, such as Active Queue Management (AQM). This paper introduces a novel optimal AQM policy to operate in networks that adopt the High Speed TCP (HSTCP) variant as their transport protocol. The effectiveness of various optimal controllers is evaluated and the performance of the new policy is compared to that of Random Early Detection (RED) policy. Results, derived via simulation, reveal the advantages of adopting HSTCP-H2 in large bandwidth-delay product networks. <s> BIB005 </s> A Review of Router based Congestion Control Algorithms <s> IV. SIGNIFICANCE OF ROUTER BASED CONGESTION CONTROL <s> Queue management schemes at the routers and congestion avoidance schemes at the end points cooperate to provide good congestion solutions in computer networks. While queue management schemes are still being developed, research on congestion avoidance has come a long way to serve the bandwidth requirement of the networks (e.g. high speed networks, data centers, etc.) at the order of 10Gbps. Because of considerable lack on the evaluation research work, there is no consensus on the choice of the queue management algorithms over these networks. To the best of our knowledge, this is the first work that presents experimental evaluation of the effect of various queue management schemes on high speed TCP variants in realistic 10Gbps network environment. Evaluation of queue management schemes such as Drop-tail, RED, CHOKe, and SFB are presented for popular high speed TCP variants such as TCP-RENO, HSTCP, and CUBIC over CRON [1], a real 10Gbps high speed network testbed. Performance results are presented for several important metrics of interests such as link utilization, fairness, delay, packet drop rate, and computational complexity. The presented work supports further research work on the design and deployment issues of queue management schemes for high speed networks. <s> BIB006 </s> A Review of Router based Congestion Control Algorithms <s> IV. SIGNIFICANCE OF ROUTER BASED CONGESTION CONTROL <s> The Internet is no longer controlled by a single TCP algorithm. Due to the scalability limitations of traditional TCP algorithms, a plethora of new high-speed TCP congestion control algorithms have been proposed and deployed. Having no standards to follow, these algorithms are ad hoc fixes and some of them have been adopted by various operating system vendors. This begs the question of whether these heterogeneous TCP algorithms are fair or compatible both to each other and to the traditional TCP algorithm. Our simulation study shows that most of the TCP algorithms are surprisingly highly unfair to each other or to the traditional TCP algorithm under several well-known queue management (QM) schemes. This calls for new approaches to QM schemes, and a recently proposed QM scheme, AFpFT, is hence included in the study. Promisingly, AFpFT helps battle the TCP heterogeneity and enforce fairness among the various considered TCP variants. We believe this study sheds new lights on TCP and QM designs. <s> BIB007
Extensive research works have been done in the area of congestion control by considering the two approaches independently. In this section, we discussed the reasons, to support our view, that why the two approaches should be studied together. As network is considered as a distributed system, any problem arises in such a system requires a distributed solution. Thus for good congestion control in the networkwe also need a solution distributed at source as well as router ends. Braden et al  (1998) have commented that TCP congestion avoidance mechanisms, while necessary and powerful, are not sufficient to provide good service in all circumstances. There is a limit to how much control can be accomplished from the edges of the network. Some mechanisms are needed in the routers to complement the end point congestion avoidance mechanisms.Su et al BIB001 (2000) found that congestion control is performed mainly by transport protocols at end hosts. However, as continuous media multicast applications (which usually do not deploy TCP for congestion control) become widely deployed on the Internet, it becomes difficult to exclusively rely on end hosts to perform end-to-end congestion control. It has been agreed upon that the network itself must now participate in congestion control and resource management.The Internet Engineering Task Force (IETF) has advocated the Deployment of active queue management mechanisms at routers to detect incipient congestion and to explicitly signal traffic sources before congestion actually occurs.Hollot et al BIB002 (2003) found that as the number of users and the size of the network increases, End-to end based congestion control methods are expected to result in unsatisfactory performance like multiple packet losses and low link utilization. Network algorithms such as active queue management (AQM), executed bynetwork components such as routers, detect network congestion, packet losses, or incipient congestion, and inform traffic sources (either implicitly or explicitly). In response, source algorithms adjust the source's data-sending rate into the network. Paganini et al BIB003 (2005) emphasized that congestion control mechanisms in the Internet consist of the congestion window algorithms of TCP, running at end-systems, and active queue management (AQM) algorithms at routers. AQM approaches are used in addition to TCP to obtain high network utilization, smallamounts of queuing delay, and some degree of fairness among users.Sonkoly et al BIB004 (2009) commented that in order to get efficient network operation and to avoid congestion collapse, end-to-end congestion control mechanism is an important component. However, the dynamic behaviour of the network is not exclusively affected by these mechanisms but network routers also play important roles. Active Queue Management schemes were proposed in order to avoid congestion at the routers by means of efficient buffer management.Santi et al BIB005 (2011) commented that Endto-end based Congestion control mechanism have not been by themselves sufficient to avoid congestion since their sources exert limited control in the aggregate network traffic in the presence of unresponsive flows. Therefore, congestion control must also rely on additional mechanisms, such as Active Queue Management (AQM). Such a mechanism notifies TCP senders of incipient congestion by dropping or marking packets.Xue et al BIB006 (2012) considered the cooperation of both end-to-end based and router based congestion control mechanisms to provide good congestion solutions in computer networks.Eshete et al BIB007 (2012) commented that router based mechanisms are designed to make earlier packet drop decisions at congested routers before buffer at routerbecomes full, which allow TCP sources to gracefully slow down their sending rate, thus improving network utilization. Thus from the above discussion it can be inferred that both the approaches for handling congestion are complementary to each other.