Control In High-speed Networks Research Articles

Congestion Control in High Speed Networks Using Fuzzy Logic Control

The tremendous growth of the internet and the advances of computer technology have been pushing forward computer networks for high speed and broad bandwidth. As the internet becomes increasingly heterogeneous, the issue of congestion control becomes ever more important. The large increase in traffic demands and the relentless demand for network capacity have produced a need for new flexible types of congestion control. Congestion being a non-linear and dynamic problem in the Internet Fuzzy Controller can be used to deal with this problem. Congestion can be controlled at core and bottleneck router differently. Fuzzy logic helps to increase throughput, reduction in packet drop and delays.

Integrated Control in High-Speed Networks using constrained Model Predictive Control

This paper studies congestion control in high-speed communication networks using Model Predictive Control (MPC). Network traffic is assumed to consist of best-effort and priority traffic sources. An integrated controller consisting of two control parts is designed. The controller calculates the capacity for priority sources and the input rate of best-effort sources. MPC is desirable as it can take into account the constraints on the finite buffer and input rate, as well as deal very well with systems with time delays.

Hybrid congestion control for high-speed networks

Nowadays, more and more applications require fast transfer of massive data over networks, and the emergence of high-speed networks provides an ideal solution to this challenge. Due to the limitations of the conservative congestion control algorithm, the standard TCP is no longer appropriate for high-speed networks to efficiently utilize the bandwidth resources. Therefore, several high-speed TCP variants have been suggested to conquer the problem. However, although these protocols perform successfully to improve the bandwidth utilization, they still have the weakness on the performance such as RTT-fairness, TCP-friendliness, etc. In this paper, we propose HCC TCP, a hybrid congestion control algorithm using the synergy of delay-based and loss-based approach for the adaptation to high speed and long distance network environment. The algorithm uses queuing delay as the primary congestion indicator, and adjusts the window to stabilize around the size which can achieve the full utilization of available bandwidth. On the other hand, it uses packet loss as the second congestion indicator, and a loss-based congestion control strategy is utilized to maintain high bandwidth utilization in the cases that the delay-based strategy performs inefficiently in the networks. The two approaches in the algorithm are dynamically transferred into each other according to the network status. We finally perform simulations to verify the properties of the proposed HCC TCP. The simulation results demonstrate HCC TCP satisfies the requirements for an ideal TCP variant in high-speed networks, and achieves efficient performance on throughput, fairness, TCP-friendliness, robustness, etc.

Unreliable transport protocol using congestion control for high-speed networks

Currently there is no control for the real-time traffic of multimedia applications using UDP (User Datagram Protocol) in high-speed networks. Therefore, although a number of high-speed TCP (Transmission Control Protocol) protocols have been developed for gigabit-speed (or faster) links, the real-time traffic could also congest the network and result in unfairness and throughput degradation of TCP traffic. In this paper, a new unreliable transport protocol, FAST DCCP, is presented for the real-time traffic in high-speed networks. FAST DCCP is based on the DCCP protocol and adopts the FAST scheme to realize congestion control. Some modifications have been made to the mechanisms inherited from DCCP so as to let the proposed protocol can efficiently operate under a large size window. In addition, an enhanced protocol, EEFAST DCCP, using the measurements of one-way delay to dynamically adjust the window size is also proposed to improve the throughput of FAST DCCP with the effect of reverse traffic. Simulation results show that FAST DCCP not only can satisfy the requirements of real-time data delivery, but also perform well in bandwidth utilization and fairness in high-speed networks. Meanwhile, EEFAST DCCP is able to effectively conquer the throughput degradation caused by the reverse traffic.

A proactive mechanism for quality of service control in high speed networks

The internet offers best effort service only. The problem of providing Quality of Service (QoS) control to multimedia flows in a congested router is challenging in this scenario. A novel Active Queue Management (AQM) mechanism is proposed for use at the router. The design and modelling of this queue-based AQM is presented. The buffer at the outgoing link is a simple First-In-First-Out, shared by packets belonging to n flows. A packet-dropping scheme with a single threshold is applied. As against Random Early Detection (RED), which uses the average queue size to control dropping, this work uses instantaneous queue size for making the decisions. This improves the buffer utilisation at the IP routers. The mechanism helps multimedia applications by giving preferential treatment to their flows. The mechanism also considers inter-protocol fairness by reducing loss rates of Transmission Control Protocol (TCP) flows. By doing this, the scheme implements the fair queuing policy. The scheme is stateless and easy to implement. Simulation results indicate that the new service model gives a better than best-effort treatment to the flows that require good QoS.

Adaptive Hurst Index Estimator Based on Wavelet

The measurement studies show that the burstiness of packet traffic in LAN as well as WAN is associated with self-similar and long-range dependency, and Hurst index is the key value of this model representing the burstiness of traffic. With the analysis in discrete wavelet domain, the nature of the wavelet coefficients and their statistical properties are proposed. Then an adaptive, efficient unbiased estimator of Hurst index based on multiresolution wavelet analysis and weighted regression is presented. Simulation results based on fractal Gaussian noise and real traffic data reveal the proposed approach shows more adaptiveness, accuracy and robustness than traditional estimators which has only O(N) computation. Thus this estimator can be applied to the application of traffic management and real-time control in high-speed networks.

Proactive congestion control for high speed networks

The next generation high speed networks which are characterized by large bandwidth propagation delay products are expected to support applications with diverse traffic characteristics and Quality of Service (QoS) requirements. Since statistical multiplexing is employed in these networks, congestion control and avoidance mechanisms are required for the delivery of QoS required by various applications. A number of reactive flow control schemes have been developed in the past for best effort applications. It has been well established that these schemes are not effective for networks with large bandwidth propagation delay products as the feedback information generated in the network can be outdated by the time it reaches the sources. In this paper, this problem (referred to as the bandwidth mismatch problem) is investigated and a proactive feedback (PF) based flow control scheme which attempts to eliminate the bandwidth mismatch problem by generating and transmitting early feedback messages is introduced. With cooperation among the network nodes and sources, the PF based flow control scheme can significantly increase the QoS delivered to the best effort applications. In addition to the increased level of delivered QoS, fair rate allocations to the best effort applications are also possible since the efficiency of the scheme becomes independent of the length of the propagation delays, once the bandwidth mismatch is eliminated.

Quality of service control in high-speed networks [Book Review

Quality of service control in high-speed networks [Book Review

Perturbation Analysis for Stochastic Fluid Queueing Systems

Recent study for congestion control in high speed networks indicates that the derivative information for the congestion at the common buffer for multiple sources could be useful in achieving efficient and fair allocation of the bandwidth (Kelly, 1997; Kelly et al., 1998). In this paper we present an algorithm that estimates such derivatives for multiple on-off sources. The algorithm has its root in the infinitesimal perturbation analysis (IPA) for the classical queueing systems. Although the traditional IPA algorithm does not give unbiased derivative estimates for multi-class arrivals, we are able to prove the unbiasedness in the case of multi-class ON-OFF sources. The results in this paper may motivate a new look at the end-to-end congestion control issue.

Adaptive rate control in high-speed networks: performance issues

It is well established that increased network transmission speed reduces the effectiveness of feedback-based adaptive rate control mechanisms, due to the increased bandwidth propagation delay product. In this environment, differences in the propagation delays associated with the controlled sources become larger when measured in slots (transmission time of information unit), potentially inducing substantially diversified performance metrics. One of the objectives in this work is to quantify the potential unfairness as well as the reduced effectiveness of this rate control scheme in the presence of non-zero propagation delays. As the network speed increases, it is also expected that traffic sources will seem to be slower due to the relative increase of the information generation time and/or the decrease of the portion of the bandwidth required by a specific source. The other objective in this work is to investigate and quantify the expected increased effectiveness of this rate control scheme in the presence of non-zero propagation delays as the traffic sources become slower. The studies are carried out by formulating queuing models and evaluating the per-session cell loss probabilities and they are supported by numerical results.

Diffusion approximations for a single node accessed by congestion-controlled sources

We consider simple models of congestion control in high-speed networks, and develop diffusion approximations which could be useful for resource allocation. We first show that, if the sources are ON-OFF type with exponential ON and OFF times, then, under a certain scaling, the steady-state distribution of the number of active sources can be described by a combination of two appropriately truncated and renormalized normal distributions. For the case where the source arrival process is Poisson and the service times are exponential, the steady-state distribution consists of appropriately normalized and truncated Gaussian and exponential distributions. We then consider the case where the arrival process is a general renewal process with finite coefficient of variation and service-time distributions that are phase type, and show the impact of these distributions on the steady-state distribution of the number of sources in the system. We also establish an insensitivity to service-time distribution when the arrival process is Poisson. We use these results to relate the capacity of a bottleneck node to performance measures of interest for best effort traffic.

Fuzzy neural network based traffic prediction and congestion control in high-speed networks

Congestion control is one of the key problems in high-speed networks, such as ATM. In this paper, a kind of traffic prediction and preventive congestion control scheme is proposed using neural network approach. Traditional predictor using BP neural network has suffered from long convergence time and dissatisfying error. Fuzzy neural network developed in this paper can solve these problems satisfactorily. Simulations show the comparison among no-feedback control scheme, reactive control scheme and neural network based control scheme.

A control-theoretic approach to the design of an explicit rate controller for ABR service

We present a control-theoretic approach to the design of closed-loop rate-based flow control in high-speed networks. The proposed control uses a dual proportional-plus-derivative controller, where the control parameters can be designed to ensure the stability of the traffic patterns and propagation delays. We show how the control mechanism can be used to design a controller to support ABR service based on feedback of explicit rates (ERs). We demonstrate the excellent transient and steady-state performance of the controller through a number of examples. We also show experimental results that have been obtained from our asynchronous transfer mode (ATM) testbed, which consists of two interconnected ATM LANs, one located in Princeton, NJ, and the other in Berlin, Germany, with an all-software ER-controller implementation.

Approximations for the Disjoint Paths Problem in High-Diameter Planar Networks

We consider the problem of connecting distinguished terminal pairs in a graph via edge-disjoint paths. This is a classical NP-complete problem for which no general approximation techniques are known; it has recently been brought into focus in papers discussing applications to admission control in high-speed networks and to routing in all- optical networks. In this paper we provideO(logn)-approximation algorithms for two natural optimization versions of this problem for the class of nearly Eulerian, uniformly high-diameter planar graphs, which includes two-dimensional meshes and other common planar interconnection networks. We give anO(logn)-approximation to the maximum number of terminal pairs that can be simultaneously connected via edge-disjoint paths, and anO(logn)-approximation to the minimum number of wavelengths needed to route a collection of terminal pairs in the “optical routing” model considered by Raghavan, Upfal, and others. The latter result improves on anO(log2n)-approximation for the special case of the mesh obtained independently by Aumann and Rabani. For both problems theO(logn)-approximation is a consequence of anO(1)-approximation for the special case when all terminal pairs are roughly the same distance apart. Our algorithms make use of a number of new techniques, including the construction of a “crossbar” structure in any nearly Eulerian planar graph, and develops some connections with classical matroid algorithms.

Bandwidth allocation and call admission control in high-speed networks

The authors discuss the broad issue of bandwidth allocation and call admission control (CAC) in high-speed networks, focusing on asynchronous transfer mode technology. It is maintained that despite the considerable amount of high-quality work carried out in this area, the debate surrounding these issues is not yet resolved. The complexity of dealing with a wide variety of as yet unknown user traffic types, as well as the evolving architecture of networks, means that currently proposed solutions are only an intermediate step of the design process. The authors discuss the nature of user traffic and illustrate how it can impact the debate on the quality of service, concentrating on some "equivalent bandwidth" type CAC strategies. Also discussed is a method which uses diffusion approximations. Finally, the authors discuss the novel issue of evaluating the overload created by the CAC procedure itself on network nodes. The article is complemented by several numerical and simulation results which illustrate the discussion.

A VLSI fuzzy expert system for real-time traffic control in ATM networks

Concerns a fuzzy logic-based system which has been purposely designed to achieve real-time traffic control in high-speed networks using the asynchronous transfer mode (ATM) technique. One of the most critical functions is "policing", which has the task of ensuring that each user source complies with the traffic parameters negotiated in the call setup to avoid network congestion. This function is difficult to implement on account of certain conflicting requirements such as selectivity and responsiveness. This is confirmed by the severe limits affecting the most popular mechanisms proposed so far, based on conventional logic. The capacity to formalize approximate reasoning processes offered by fuzzy logic is exploited to derive rules of behavior for a policer starting from the know-how of an expert. We address two key issues related to the implementation of the fuzzy policer. The first focuses on the possibility of hardware implementation of the mechanism using VLSI technology; we present the design of a VLSI fuzzy processor which exhibits a level of performance of over 3 MFLIPS. The second issue concerns the suitability of applying the fuzzy policer to the policing of several classes of sources to reach high levels of cost effectiveness and scalability.

Link capacity allocation and network control by filtered input rate in high-speed networks

We study link capacity allocation for a finite buffer system to transmit multimedia traffic. The queueing process is simulated with real video traffic. Two key concepts are explored in this study. First, the link capacity requirement at each node is essentially captured by its low-frequency input traffic (filtered at a properly selected cut-off frequency). Second, the low-frequency traffic stays intact as it travels through a finite-buffer system without significant loss. Hence, one may overlook the queueing process at each node for network-wide traffic flow in the low-frequency band. We propose a simple, effective method for link capacity allocation and network control using on-line observation of traffic flow in the low-frequency band. The study explores a new direction for measurement-based traffic control in high-speed networks. >

Bandwidth allocation and access control in high-speed networks

The problem of bandwidth allocation and access regulation arises in the congestion control of Broadband ISDN networks. This paper assumes that a single user, described by an on-off fluid model, is connected to the network via a leaky bucket access control mechanism. The bandwidth allocated to this user and the leaky bucket parameters are to be selected so as to guarantee a negotiated level of delay probability at the access point and packet loss probability in the network which is modelled as an output buffer. The design problem is to minimize the allocated bandwidth subject to service guarantees and stability conditions for the input and output buffers. We provide a desirable feasible solution to the design problem. The paper studies the effect of non-conforming users on the network performance using the leaky bucket access control corresponding to this feasible solution. We provide expressions that quantify the impact of the leaky bucket parameters in access regulation and the worst-case queueing behavior at the output buffer. Finally, we discuss the extension of this methodology to the multiple leaky buckets case.

A Two-Level Flow Control Scheme for High Speed Networks

New applications such as multimedia remote conferencing demand network transport services with performance guarantees. At the same time, new networking technologies such as ATM are gearing towards providing services on a reservation-and-guarantee basis. In the light of the new application and networking environments, it seems necessary to revisit many of the transport protocol issues in search for more efficient ways to address them. This paper proposes using an explicit rate control together with a simple window control for flow control in high-speed networks with resource reservations. The design justifications, the evaluation study, and the implementation results are presented. Particularly, the idea of hard ACK and soft ACK in the context of end-to-end flow control is explored through simulation and the results are discussed.

Effective bandwidth of general Markovian traffic sources and admission control of high speed networks

A prime instrument for controlling congestion in a high-speed network is admission control, which limits calls and guarantees a grade of service determined by delay and loss probability in the multiplexer. It is shown that for general Markovian traffic sources it is possible to assign a notional effective bandwidth to each source that is an explicitly identified, simply computed quantity with provably correct properties in the natural asymptotic regime of small loss probabilities. It is the maximal real eigenvalue of a matrix that is directly obtained from the source characteristics and the admission criterion, and for several sources it is simply additive. Both fluid and point process models are considered. Numerical results show that the acceptance set for heterogeneous classes of sources is closely approximated and conservatively bounded by the set obtained from the effective bandwidth approximation. The bandwidth-reducing properties of the leaky bucket regulator are exhibited numerically.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>