Adaptive predictive congestion control of high-speed ATM networks

This paper proposes an auto regressive moving average (ARMAX)-based adaptive control methodology to prevent congestion in high-speed asynchronous transfer mode (ATM) networks. An adaptive controller is developed to control traffic where sources adjust their transmission rates in response to the feedback information from the network switches. Specifically, the buffer dynamics at a given switch is modeled as a nonlinear discrete-time system and an ARMAX controller is designed so as to predict the explicit values of the transmission rates of the sources so as to prevent congestion. Tuning methods are provided for the unknown coefficients of the ARMAX model to estimate the unpredictable and statistically fluctuating network traffic. Mathematical analysis is given to demonstrate the stability of the closed-loop system so that a desired quality of service (QoS) can be guaranteed. The QoS is defined in terms of cell loss ratio (CLR), transmission delay and buffer utilization. We derive design rules mathematically for selecting the parameters of the ARMAX algorithm such that the desired performance is guaranteed during congestion and potential tradeoffs are shown. Simulation results are provided to justify the theoretical conclusions for multiple source/single switch scenarios using both ON/OFF and MPEG data. The performance of the proposed congestion control scheme is also evaluated in the presence of feedback delays for robustness considerations.     

A new feedback congestion control policy for long propagationdelays

This paper presents a new feedback congestion control mechanism for the flow control of the best-effort available bit rate (ABR) traffic in ATM networks. This new mechanism belongs to the class of feedback control schemes that ensure no data losses and operate based on simple `stop' and `start' signals. A novelty presented by this paper is a methodology which, for a given set of desired properties, leads to the specification of the corresponding control algorithm. For the case of a single connection, the algorithm can operate with the theoretically minimum possible buffer size. Interestingly, the algorithm obtained has a different structure than the previous schemes; it does not operate based on fixed high and low thresholds. A new congestion control mechanism is subsequently derived for the flow control of multiple connections. The new scheme is exercised hop-by-hop and on a per-connection basis. This scheme allows connections to share memory and bandwidth resources efficiently within the network. The performance of the new scheme is also presented, and its statistical multiplexing efficiency is demonstrated. The measures investigated include buffer occupancy, average delay, overhead due to the protocol signals, and sustained throughput. In the case of long propagation delays, the buffer savings achieved by the new scheme are substantial     

A Unified Approach to Congestion Control and Node-Based Multipath Routing

The paper considers a TCP/IP-style network with flow control at end-systems based on congestion feedback and routing decisions at network nodes on a per-destination basis. The main generalization with respect to standard IP is to allow routers to split their traffic in a controlled way between the outgoing links. We formulate global optimization criteria, combining those used in the congestion control and traffic engineering, and propose decentralized controllers at sources and routers to reach these optimal points, based on congestion price feedback. We first consider adapting the traffic splits at routers to follow the negative price gradient; we prove this is globally stabilizing when combined with primal congestion control, but can exhibit oscillations in the case of dual congestion control. We then propose an alternative anticipatory control of routing, proving its stability for the case of dual congestion control. We present a concrete implementation of such algorithms, based on queueing delay as congestion price. We use TCP-FAST for congestion control and develop a multipath variant of the distance vector routing protocol RIP. We demonstrate through ns2-simulations the collective behavior of the system, in particular that it reaches the desired equilibrium points.     

Evaluation of congestion control protocols for ABR traffic over ATM networks

Congestion control is very important for effective and stable operation of ATM (Asynchronous Transfer Mode) networks. Owing to the bursty and unpredictable characteristic of data network traffic, its congestion control is particularly a challenge for network researchers and designers. The ATM Forum has recently adopted rate‐based congestion control for ABR (Available Bit‐Rate) traffic which is the service class defined for data network applications. However, there is a number of congestion control schemes prevalent. ATM Forum has decided not to specify switch behaviour for ABR traffic; this has further introduced additional ambiguity. Consequently, an evaluation and comparison of the existing protocols would provide valuable guidance for network designers and engineers; it would also give insight for researchers to explore the essence of different congestion control schemes. In the first part of this paper, we investigate the effectiveness of ABR congestion control in the presence of bursty source traffic and the relationship between the burst time scale and the ABR control time scale. Two ABR congestion control schemes, the ABR Explicit Forward Congestion Indication (EFCI) and ABR Congestion Indication (CI) schemes, are compared with Unspecified Bit Rate (UBR) transport which makes no effort to control congestion. Traffic sources of various burst lengths of 100, 1000, 10000, and an equal mix of 100 and 10000 ATM cells are used in simulations. It is found that ABR congestion control schemes effectively control low frequency, medium to long‐term traffic load transients. This is further supported by the result of integrating TCP over ATM congestion control schemes included in the paper. ABR control schemes do not control high frequency, short‐term load transients well, but ABR control is not necessary in such cases since short‐term transients do not require a large amount of buffering. In the second part of this paper, we evaluate and compare six rate‐based congestion control protocols including Scheme I: EFCI, Scheme II: EFCI with separate RM queues, Scheme III: CI, Scheme IV: CI with separate RM queues, Scheme V: the CAPC2 ER (Explicit Rate), and Scheme VI: the EFCI with utilization‐based congestion indication. Each scheme is simulated and compared in the LAN, WAN, and GFC (General Fairness Configuration) environments specified by the ATM Forum. Effects of varying VC (Virtual Circuits) number and changing endsystem–switch distance has been investigated. Their fairness is also compared using the GFC configuration. We have found that ER control scheme performs significantly better than the other five binary control schemes by its faster response to congestion, smoother regulation of bit‐rates, lower queueing delay, shorter buffer queue length, and fairness. Among the other five schemes, the CI scheme performs better than the EFCI scheme. Providing separate RM queues has significantly improved the EFCI scheme in the WAN environment, but has little effect on the CI scheme. Link utilization‐based congestion detection has suffered from either low utilization or an excess cell loss which is unacceptable in most data applications. Copyright © 2000 John Wiley & Sons, Ltd.     

Stability and sensitivity for congestion control in wireless mesh networks with time varying link capacities

A critical challenge for wireless mesh networks is the design of efficient transport protocols that provide high bandwidth utilization and desired fairness in the multi-hop, wireless environment. While extensive efforts have been devoted to providing optimization based, distributed congestion control schemes for efficient bandwidth utilization and fair allocation in both wireline and wireless networks, a common assumption therein is fixed link capacities. This unfortunately will limit the application scope in wireless mesh networks where channels are ever changing. In this paper, we explicitly model link capacities to be time varying and investigate congestion control problems in multi-hop wireless networks. In particular we propose a primal–dual congestion control algorithm which is proved to be trajectory stable in the absence of feedback delay. Different from system stability around a single equilibrium point, trajectory stability guarantees the system is stable around a time varying reference trajectory. Moreover, we obtain sufficient conditions for the scheme to be locally stable in the presence of delay. Our key technique is to model time variations of capacities as perturbations to a constant link. Furthermore, to study the robustness of the algorithm against capacity variations, we investigate the sensitivity of the control scheme and through simulations to study the tradeoff between stability and sensitivity.     

Design of QoS in Intelligent Communication Environments Based on Neural Network

Due to the latest developments in communication and computing, smart services and applications are being deployed for various applications such as entertainment, health care, smart homes, security and surveillance. In intelligent communication environments, the main difficulty arising in designing an efficient congestion control scheme lies in the large propagation delay in data transfer which usually leads to a mismatch between the network resources and the amount of admitted traffic. To attack this problem, this paper describes a novel congestion control scheme in intelligent communication environments, which is based on a Back Propagation (BP) neural network technique. We consider a general computer communication model with multiple sources and one destination node. The dynamic buffer occupancy of the bottleneck node is predicted and controlled by using a BP neural network. The controlled best-effort traffic of the sources uses the bandwidth, which is left over by the guaranteed traffic. This control mechanism is shown to be able to avoid network congestion efficiently and to optimize the transfer performance both by the theoretic analyzing procedures and by the simulation studies.     

On-board closed-loop congestion control for satellite-based packet-switching networks

NASA Lewis Research Center is currently investigating a satellite architecture that incorporates an on-board packet-switching capability. Because of the statistical nature of packet switching, arrival traffic may fluctuate, and thus it is necessary to integrate the congestion control mechanism as part of the on-board processing unit. This study focuses on the closed-loop reactive control. We investigate the impact of the long propagation delay on the performance, and propose a scheme to overcome the problem. The scheme uses a global feedback signal to regulate the packet arrival rate of the ground stations. In this scheme, the satellite continuously broadcasts the status of its output buffer and the ground stations respond by selectively discarding packets or by tagging the excessive packets as low-priority. The two methods are evaluated by theoretical queueing analysis and simulation. The former is used to analyse the simplified model and to determine the basic trends and bounds, and the latter is used to assess the performance of a more realistic system and to evaluate the effectiveness of more sophisticated control schemes. The results show that the long propagation delay makes the closed-loop congestion control less responsive. The broadcast information can only be used to extract statistical information. The discarding method needs carefully-chosen status information and a reduction function, and normally requires a significant amount of ground discarding to reduce the on-board packet loss probability. The tagging method is more effective since it tolerates more uncertainties and allows a larger margin of error in status information. It can protect the high-priority packets from excessive loss and fully use the down-link bandwidth at the same time.     

Performance analysis of a rate-based feedback control scheme

In this paper, we present a numerical approach to the performance study of a delayed feedback system with one congested node and multiple connections. This approach consists of modeling the feedback system as a finite quasi-birth-death process. Due to the peculiar block tridiagonal nature of its generator, efficient techniques exist for its steady-state and transient solutions. Using these techniques, we examine a simple parsimonious feedback system for issues such as throughput/loss performance, fairness, and stability. Our approach has the flexibility to study the effect of several additional factors such as asynchronous feedback, two-level control, and explicit rate notification in the presence of underlying high-priority traffic. This study brings to light the tradeoffs between system performance and the complexity of the feedback scheme. Our study shows that the time scales of correlation of the feedback system have a dominant effect on its performance. These time scales are associated with the feedback delay, the durations of active/idle periods of traffic sources, and the time scales of the underlying high-priority traffic. We also examine the effect of the time scales on the convergence time for the transient queueing system     

Engineering ATM networks for congestion avoidance

With the combination of telecommunication, entertainment and computer industries, computer networking is adopting a new method called Asynchronous Transfer Mode (ATM) networking. Congestion control plays an important role in the effective and stable operation of ATM networks. Traffic management concerns with the design of a set of mechanisms which ensure that the network bandwidth, buffer and computational resources are efficiently utilized while meeting the various Quality of Service (QoS) guarantees given to sources as part of a traffic contract. In this paper, the most widely recognized congestion control schemes for ABR service are investigated. Some of these schemes show either lack of scalability or fairness while other well‐behaved schemes may require a highly complex switch algorithm that is unsuitable for implementation in cell‐switching high‐speed ATM networks. A new and improved congestion control scheme is proposed to support the best‐effort ABR traffic. This algorithm provides the congestion avoidance ability with high throughput and low delay, in addition to achieving the max–min fairness allocation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Efficient Transmission of MPEG-2 Coded Video Traffic over ATM Networks

Video traffic is expected to account for a significant share of the traffic volume in the future asynchronous transfer mode (ATM) networks. MPEG-2 proposed by Moving Picture Expert Group is one of the most promising compression techniques for such applications. One of the critical issues in MPEG-2 is to realize effective variable bit rate (VBR) video transfer thorough ATM networks. The Leaky Bucket (LB) scheme has been widely accepted as the usage parameter control (UPC) mechanism to police the VBR sources. We proposed a new Adaptive Dynamic Leaky Bucket (ADLB) congestion control mechanism, which is based on the LB scheme. Unlike the conventional LB, the leak rate of the ADLB is controlled using delayed feedback information of available bandwidth sent by the network. This scheme allows sources to get varying amounts of bandwidth over time, while reserving a minimum guaranteed bandwidth (MCR) for the entire duration of the connection. At the time of congestion, the leak rate of the ADLB is adjusted according to the feedback indicating the currently available bandwidth to the connection. The simulation results show that the end-to-end cell transfer delay and cell loss of each source has been improved significantly.     

On hop-by-hop rate-based congestion control

The activity in building gigabit speed networks has led many researchers to re-examine the issue of congestion control. We describe a rate-based hop-by-hop congestion control mechanism in which the service rates of connections are dynamically adjusted at a switch, using feedback information provided by the neighboring switches. The desired service rate is computed based on a control equation that utilizes a model of the system with feedback information used to correct inaccuracies in the model. We use an analytical model to prove that the expected value of the queue occupancy and throughput of a controlled connection converge to the desired operating point. We also study the variation of the queue occupancy and throughput in steady-state as well as the transient response. The analytical results provide insights into how the parameter values chosen affect performance. We use simulations to compare the performance of the scheme with an equivalent end-to-end control scheme. Our analytical and simulation results show that the hop-by-hop scheme reacts faster to changes in the traffic intensity and, consequently, utilizes resources at the bottleneck better and loses fewer packets than the end-to-end scheme     

Supporting Excess Real-Time Traffic With Active Drop Queue

Real-time applications often stand to benefit from service guarantees, and in particular delay guarantees. However, most mechanisms that provide delay guarantees also hard-limit the amount of traffic the application can generate, i.e., to enforce to a traffic contract. This can be a significant constraint and interfere with the operation of many real-time applications. Our purpose in this paper is to propose and investigate solutions that overcome this limitation. We have four major goals: 1) guarantee a delay bound to a contracted amount of real-time traffic; 2)transmit with the same delay bound as many excess real-time packets as possible; 3) enforce a given link sharing ratio between excess real-time traffic and other service classes, e.g., best-effort; and 4) preserve the ordering of real-time packets, if required. Our approach is based on a combination of buffer management and scheduling mechanisms for both guaranteeing delay bounds, while allowing the transmission of excess traffic. We evaluate the “cost” of our scheme by measuring the processing overhead of an actual implementation, and we investigate its performance by means of simulations using video traffic traces.     

Performance management issues in ATM networks: traffic andcongestion control

The goal is first to introduce performance monitoring aspects of asynchronous transfer mode (ATM) networks and then to focus on traffic and congestion control schemes. To deal with this performance monitoring management, a framework for defining a generic intelligent and integrated model for network management is described. As an example of the efficiency of this intelligent management architecture, we measure the performance of a new congestion control scheme. This scheme uses the cell loss priority (CLP) bit, the explicit forward congestion indicator and the explicit backward congestion indicator. The intelligent management uses different parameters and builds a complex but efficient control scheme. We show that this new control scheme allows performance to be increased by an order of magnitude     

Performance evaluation of legacy QCN for multicast and multiple unicast traffic transmission

A multicast congestion control scheme is an interesting feature to control group communication applications such as teleconferencing tools and information dissemination services. This paper addresses a comparison between multiple unicast and multicast traffic congestion control for Carrier Ethernet. In this work, we proposed to study the quantized congestion notification (QCN), which is a layer 2 congestion control scheme, in the case of multicast traffic and multiple unicast traffic. Indeed, the QCN has recently been standardized as the IEEE 802.1Qau Ethernet Congestion Notification standard. This scheme is evaluated through simulation experiments, which are implemented by the OMNeT++ framework. This paper evaluates the reaction point start time congestion detection, feedback rate, loss rate, stability, fairness and scalability performance of the QCN for multicast traffic transmission and multiple unicast traffic transmission. This paper also draws a parallel between QCN for multicast traffic transmission and that for multiple unicast traffic transmission. Despite the benefit of integrating the multicast traffic, results show that performance could degrade when the network scales up. The evaluation results also show that it is probable that the feedback implosion problem caused by the bottlenecks could be solved if we choose to set the queue parameter Qeq threshold value at a high value, 75% of the queue capacity for instance. Copyright © 2016 John Wiley & Sons, Ltd.     

ACC: using active networking to enhance feedback congestion controlmechanisms

Active congestion control (ACC) uses active networking (AN) technology to make feedback congestion control more responsive to network congestion. Current end-to-end feedback congestion control systems detect and relieve congestion only at endpoints. ACC includes programs in each data packet that tell routers how to react to congestion without incurring the round-trip delay that reduces feedback effectiveness in wide area networks. The congested router also sends the new state of the congestion control algorithm to the endpoints to ensure that the distributed state becomes consistent. We present a model for extending feedback congestion control into an active network, apply that model to TCP congestion control, and present simulations that show that the resulting system exhibits up to 18 percent better throughput than TCP under bursty traffic. In simulations without bursty traffic, the systems behaved comparably     

Scheduling Algorithms for a Slotted Packet Switch with either Fixed or Variable Length Packets

We address the problem of congestion resolution in optical packet switching (OPS). We consider a fairly generic all-optical packet switch architecture with a feedback optical buffer constituted of fiber delay lines (FDL). Two alternatives of switching granularity are addressed for a switch operating in a slotted transfer mode: switching at the slot level (i.e., fixed length packets of a single slot) or at the burst level (variable length packets that are integer multiples of the slot length). For both cases, we show that in spite of the limited queuing resources, acceptable performance in terms of packet loss can be achieved for reasonable hardware resources with an appropriate design of the time/wavelength scheduling algorithms. Depending on the switching units (slots or bursts), an adapted scheduling algorithm needs to be deployed to exploit the bandwidth and buffer resources most efficiently.     

Power factor correction converter using delay control

A low cost universal input voltage single-controller power factor correction converter for a 200 W power supply is proposed. It consists of the PFC part followed by a DC-DC converter as in a conventional two-stage scheme. However a single PWM controller is used as in a single-stage PFC scheme. The switch in the PFC part is synchronized with the switch in the DC-DC converter and has a fixed frequency. Employing an adaptive delay scheme, the PPC switch is controlled to limit the capacitor voltage within a desired range for optimum efficiency and to reduce input current harmonic distortion. The design procedures of the delay scheme, the feedback loop, and experimented results are presented to verify the performance     

Estimation and Prediction‐Based Connection Admission Control in Broadband Satellite Systems

We apply a “sliding‐window” Maximum Likelihood (ML) estimator to estimate traffic parameters of On‐Off source and develop a method for estimating stochastic predicted individual cell arrival rates. Based on these results, we propose a simple Connection Admission Control (CAC) scheme for delay sensitive services in broadband onboard packet switching satellite systems. The algorithms are motivated by the limited onboard satellite buffer, the large propagation delay, and low computational capabilities inherent in satellite communication systems. We develop an algorithm using the predicted individual cell loss ratio instead of using steady state cell loss ratios. We demonstrate the CAC benefits of this approach over using steady state cell loss ratios as well as predicted total cell loss ratios. We also derive the predictive saturation probability and the predictive cell loss ratio and use them to control the total number of connections. Predictive congestion control mechanisms allow a satellite network to operate in the optimum region of low delay and high throughput. This is different from the traditional reactive congestion control mechanism that allows the network to recover from the congested state. Numerical and simulation results obtained suggest that the proposed predictive scheme is a promising approach for real time CAC.     

Effective control of traffic flow in ATM networks using fuzzyexplicit rate marking (FERM)

We describe the fuzzy explicit fate marking (FERM) traffic flow control algorithm for a class of best effort service, known as available bit rate (ABR), proposed by the ATM Forum. FERM is an explicit rate marking scheme in which an explicit rate is calculated at the asynchronous transfer mode (ATM) switch and sent back to the ABR traffic sources encapsulated within resource management (RM) cells. The flow rate is calculated by the fuzzy congestion control (FCC) module by monitoring the average ABR queue length and its rate of change, then by using a set of linguistic rules. We use simulation to compare the steady-state and transient performance of FERM with EPRCA (a current favourite by the ATM Forum) in the presence of high priority variable bit rate (VBR) video and constant bit rate (CBR) in both a local-area network (LAN) and a wide-area network (WAN) environment. Our experiments show that FERM exhibits a robust behavior, even under extreme network loading conditions, and ensures fair share of the bandwidth for all virtual channels (VCs) regardless of the number of hops they traverse. Additionally, FERM controls congestion substantially better than EPRCA, offers faster transient response, leads to lower end-to-end delay and better network utilization     

Definition and performance analysis of a simple, ABR-likecongestion control scheme for satellite ATM networks with guaranteedloss performance

We describe an ATM system architecture for satellite communications. The proposed architecture includes on-board switching, and supports the ATM traffic categories defined in previous specifications. In this framework, a critical issue is the control of congestion phenomena. In particular, the application of feedback-based control strategies to a satellite network is critical due to the peculiarities of such an environment: very large propagation delay, expensive transfer capacity, and limited on-board processing capability. The available bit rate (ABR) is the ATM service category handled according to a reactive congestion control (RCC). The focus of this paper is the definition of an RCC that is fully compatible with the standard ABR protocols, and that takes into account the constraints of the satellite environment. We also derive an analytical model that allows us to evaluate the performance of the proposed scheme and to dimension the system. The analytical model is validated with simulations