Survey of congestion control techniques for an ATM network

The emerging broadband integrated services digital network is expected to adopt ATM (Asynchronous Transfer Mode) as the transport network. This new network must support several classes of service with varying delay and loss requirements. It must also operate with link speeds in the hundreds of megabits per second and be scalable up to potential link speeds on the order of gigabits per second. The requirements to support multiple services and high speed make the congestion control in an ATM network difficult. This paper reviews sorne of the techniques for prevention and control of congestion in an ATM network

Resource Allocation Methodology for Internet Heterogeneous Traffic

The mode of operation of internet can lead to congestion which, in turn, leads to degradation in the quality of service (QoS). Congestion can be seen as overflow in the input and/or output buffers of switches at a node. Research issue relating to internet services is determining the optimum network resources - in terms of transmission link bandwidth and buffer capacity in switches - that are required for heterogeneous internet traffic which guarantees a given QoS, even under high network loading conditions.This paper, therefore, presents a method for determining the optimum internet resources required for heterogeneous (data and voice only) traffic services to guarantee given QoS requirement

Reduction of bandwidth requirement by traffic dispersion in ATM networks

The problem of bandwidth allocation and routing in Virtual Path (VP) based Asynchronous Transfer Mode (ATM) networks was studied. As an efficient way to facilitate the network management, VP concept has been proposed in the literature. Traffic control and resource management are simplified in VP based networks. However, a priori reservation of resources for VP\u27s also reduces the statistical multiplexing gain, resulting in increased Call Blocking Probability (CBP);The focus of this study is on how to reduce CBP (or equivalently, how to improve the bandwidth utilization for a given CBP requirement) by the effective bandwidth allocation and routing algorithms. Equivalent capacity concept was used to calculate the required bandwidth by the call. Each call was represented as a bursty and heterogeneous multimedia traffic;First, the effect of traffic dispersion was explored to achieve more statistical gain. Through this study, it was discovered how the effect of traffic dispersion varies with different traffic characteristics and the number of paths. An efficient routing algorithm, CED, was designed. Since traffic dispersion requires resequencing and extra signaling to set up multiple VC\u27s, it should be used only when it gives significant benefits. This was the basic idea in our design of CED. The algorithm finds an optimal dispersion factor for a call, where the gain balances the dispersion cost. Simulation study showed that the CBP can be significantly reduced by CED;Next, this study provides analysis of the statistical behavior of the traffic seen by individual VP, as a result of traffic dispersion. This analysis is essential in estimating the required capacity of a VP accurately when both multimedia traffic and traffic dispersion are taken into account. Then analytical models have been formulated. The cost effective design and engineering of VP networks requires accurate and tractable mathematical models which capture the important statistical properties of traffic. This study also revealed that the load distribution estimated by equivalent capacity follows Gaussian distribution which is the sum of two jointly Gaussian random variables. For the analysis of load distribution when CED is used, we simplified multiple paths as identical paths using the idea of Approximation by Single Abstract Path (ASAP), and approximated the characteristics of the traffic seen by individual VP. The developed analytical models and approximations were validated in the sense that they agreed with simulation results

A logic-level simulation of the ATMSWITCH : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Computer Science at Massey University

ATM networks are intended to provide a "one-size-fits-all" solution to a variety of data communication needs, from low speed, delay-insensitive to high-speed, delay-intolerant. The basic ATM protocol certainly delivers traffic within this broad range, but it does not address the quality of service requirements associated with the various type of traffic. The ATMSW1TCH is designed to use two different mechanisms to provide the quality of service for the various type of traffic. It treats the cells according to their connected virtual channel type and services them as predefined scheme. The ATMSWITCH architecture is a shared-memory and output buffer strategy switch. The switch has been designed much of buffer location and identification can occur in parallel with the 12ns read/write cycle time required to buffer the cell data. The problem is essentially one of design circuitry so that buffer location and identification are as short as possible. The present project has therefore been intended to measure the number of clock cycles required to perform the buffer maintenance activities, and to determine whether the logic speed required to fit this number of clock cycles into the 12ns window is feasible using current technology. The simulated result and timing analysis shows that 10 clock cycles are required during 12ns buffer read and write time, and a reasonable clock speed is 1.2ns per clock cycle

System level performance of ATM transmission over a DS-CDMA satellite link.

PhDAbstract not availableEuropean Space Agenc

Some aspects of traffic control and performance evaluation of ATM networks

The emerging high-speed Asynchronous Transfer Mode (ATM) networks are expected to integrate through statistical multiplexing large numbers of traffic sources having a broad range of statistical characteristics and different Quality of Service (QOS) requirements. To achieve high utilisation of network resources while maintaining the QOS, efficient traffic management strategies have to be developed. This thesis considers the problem of traffic control for ATM networks. The thesis studies the application of neural networks to various ATM traffic control issues such as feedback congestion control, traffic characterization, bandwidth estimation, and Call Admission Control (CAC). A novel adaptive congestion control approach based on a neural network that uses reinforcement learning is developed. It is shown that the neural controller is very effective in providing general QOS control. A Finite Impulse Response (FIR) neural network is proposed to adaptively predict the traffic arrival process by learning the relationship between the past and future traffic variations. On the basis of this prediction, a feedback flow control scheme at input access nodes of the network is presented. Simulation results demonstrate significant performance improvement over conventional control mechanisms. In addition, an accurate yet computationally efficient approach to effective bandwidth estimation for multiplexed connections is investigated. In this method, a feed forward neural network is employed to model the nonlinear relationship between the effective bandwidth and the traffic situations and a QOS measure. Applications of this approach to admission control, bandwidth allocation and dynamic routing are also discussed. A detailed investigation has indicated that CAC schemes based on effective bandwidth approximation can be very conservative and prevent optimal use of network resources. A modified effective bandwidth CAC approach is therefore proposed to overcome the drawback of conventional methods. Considering statistical multiplexing between traffic sources, we directly calculate the effective bandwidth of the aggregate traffic which is modelled by a two-state Markov modulated Poisson process via matching four important statistics. We use the theory of large deviations to provide a unified description of effective bandwidths for various traffic sources and the associated ATM multiplexer queueing performance approximations, illustrating their strengths and limitations. In addition, a more accurate estimation method for ATM QOS parameters based on the Bahadur-Rao theorem is proposed, which is a refinement of the original effective bandwidth approximation and can lead to higher link utilisation