ATM Network Performance Research Articles

Handover Optimization in Wireless Microcellular ATM Networks

Microcellular solutions in wireless ATM networks increase the network traffic control as a result of frequent handover requests. The blocking probability or the forced termination probability presents a quality of service criterion for evaluation of certain handover techniques. This paper presents a handover protocol that can avoid cell loss and guarantee cell sequence, and a two layer wireless call admission control is studied, using Markov state diagrams, in order to optimize the performance of wireless ATM networks.

Performance improvement of dynamic buffered ATM switch

Performance of ATM networks depends on switch performance and architecture. This paper presents a simulation study of a new dynamic allocation of input buffer space in ATM switching elements. The switching elements are composed of input and output buffers which are used to store received and forwarded cells, respectively. Efficient and fair use of buffer space in an ATM switch is essential to gain high throughput and low cell loss performance from the network. In this paper, input buffer space of each switching element is allocated dynamically as a function of traffic load. A shared buffer pool is provided with threshold-based virtual partition among input ports, which supplies the necessary input buffer space as required by each input port. The system behaviour under varying traffic loads has investigated using a simulation program. Also, a comparison with a static allocation scheme shows that the threshold based dynamic buffer allocation scheme ensures an increased network throughput and a fair share of the buffer space even under bursty loading conditions.

Modeling techniques for VBR video: feasibility and limitations

Many techniques have been proposed to evaluate the performance of ATM networks carrying VBR video traffic. The choice among these techniques may not be straightforward for researchers in other areas of computer networks. The aim of this work is to focus on three techniques that are based on two source models, and present a comparative study for them. As it will be shown, it is very difficult to have a perfect modeling technique that fits into all situations. The added complexity of multimedia traffic will make such task unfeasible. Also, a look into the situations of advantageous applicability of each one of these techniques, along with possible limitations and drawbacks will be given.

Southampton ATM network performance, 2nd ed. [Book Review

Southampton ATM network performance, 2nd ed. [Book Review

Performance comparison criteria for ATM switch models

Performance of ATM networks will depend on switch performance and architecture. In this paper a set of 11 questions is presented in order to be able to study performance. It is necessary to clearly identify the main characteristics of switch architecture and traffic which are considered so as to be able to derive relevant comparisons. The questions concern the level of study, the placement of the memory, the monopath or multipath architecture, the uniformity of input stream, the destination hypotheses, the routing rules inside the switch, the eventual resequencing, etc. In case of cell level study and output buffers, the answers to the six main questions lead to a tree including 14 realistic switch and traffic types. A survey of the modelling method for these cases is then presented. In order to illustrate the methodology, few results are given in some of the realistic cases and some general conclusions appear to be pertinent: importance of traffic asymmetry, best performance for multipath switches, use of path reservations inside the switch.

Bandwidth-demand prediction in virtual path in ATM networks using genetic algorithms

The concept of Virtual Paths (VP) is a powerful technique to improve the transmission efficiency in ATM networks. Transmission efficiency can be improved by dynamically changing the bandwidths of the VPs, based on the demand. Intelligent controllers, which predict bandwidth-demand patterns to enable better VP management, have the potential to revolutionize ATM network performance. We present a scheme based on the Evolutionary Genetic Approach to predict the bandwidth-demand patterns in VPs. The efficiency of this approach, quantified in terms of the Degree of Learning (DoL), is evaluated through simulation and the results are presented.

Performance analysis of data packet discarding in ATM networks

Data performance in ATM networks should be measured on the packet level instead of the cell level, since one or more cell losses within each packet is equivalent to the loss of the packet itself. Two packet-level control schemes, packet tail discarding and early packet discarding, were proposed to improve data performance. In this paper, a new stochastic modeling technique is developed for performance evaluation of two existing packet-discarding schemes at a single bottleneck node. We assume that the data arrival process is independent of the nodal congestion, which may represent the unspecified bit-rate traffic class in ATM networks, where no end-to-end feedback control mechanism is implemented. Through numerical study, we explore the effects of buffer capacity, control threshold, packet size, source access rate, underlying high-priority real-time traffic, and loading factor on data performance, and discuss their design tradeoffs. Our study shows that a network system can he entirely shut down in an overload period if no packet-discarding control scheme is implemented, under the assumption that there are no higher layer congestion avoidance schemes. Further, unless with sufficiently large buffer capacity, early packet discarding (EPD) always outperforms packet tail discarding (PTD) significantly under most renditions. Especially under the overload condition, EPD can always achieve about 100% goodput and 0% badput, whereas the PTD performance deteriorates rapidly. Among all the factors, the packet size has a dominant impact on EPD performance. The optimal selection of the EPD queue control threshold to achieve the maximum goodput is found to be relatively insensitive to traffic statistics.

Transmission of MPEG-2 video streams over ATM

Experiments investigated the relationship between MPEG video quality and ATM network performance. Preliminary results reveal the effects of network impairments on video quality for MPEG-2 transport streams delivered over ATM. The issues in mapping variable-rate MPEG to ATM are also examined, including the trade-off between bandwidth savings and video quality.

Performance of ATM networks under hybrid ARQ/FEC error control scheme

In ATM networks, fixed-length cells are transmitted. A cell may be discarded during the transmission due to buffer overflow or detection of errors. Cell discarding seriously degrades transmission quality. This paper analyzes a hybrid automatic repeat request/forward error control (ARQ/FEC) cell-loss recovery scheme that is applied to virtual circuits (VCs) of ATM networks. FEC is performed based on a simple single-parity code, while a Go-Back-N ARQ is employed on top of that. Both throughput efficiency and reliability analysis of the hybrid scheme are presented. In the process we investigate the interactive effects of the network parameters (number of transit nodes, traffic intensity, ARQ packet length, ...) on the performance. The analysis provides a method for optimizing the FEC code size for a given network specification.

Asymptotically achievable performance in ATM networks

The primary objective in the present paper is to gain fundamental understanding of the performance achievable in ATM networks as a function of the various system characteristics. We derive limit theorems that characterize the achievable performance in terms of the offered traffic, the admissible region, and the revenue measure. The insights obtained allow for substantial simplifications in the design of real-time connection admission control algorithms. In particular, we describe how the boundaries of admissible regions with convex complements may be linearized - thus reducing the admissible region - so as to obtain a convenient loss network representation. The asymptotic results for the achievable performance suggest that the potential reduction in revenue is immaterial in high-capacity networks. Numerical experiments confirm that the actual reduction is typically negligible, even in networks of moderate capacity.

Asymptotically achievable performance in ATM networks

The primary objective in the present paper is to gain fundamental understanding of the performance achievable in ATM networks as a function of the various system characteristics. We derive limit theorems that characterize the achievable performance in terms of the offered traffic, the admissible region, and the revenue measure. The insights obtained allow for substantial simplifications in the design of real-time connection admission control algorithms. In particular, we describe how the boundaries of admissible regions with convex complements may be linearized - thus reducing the admissible region - so as to obtain a convenient loss network representation. The asymptotic results for the achievable performance suggest that the potential reduction in revenue is immaterial in high-capacity networks. Numerical experiments confirm that the actual reduction is typically negligible, even in networks of moderate capacity.

Transmission of MPEG-2 video streams over ATM

Experiments investigated the relationship between MPEG video quality and ATM network performance. Preliminary results reveal the effects of network impairments on video quality for MPEG-2 transport streams delivered over ATM. The issues in mapping variable-rate MPEG to ATM are also examined, including the trade-off between bandwidth savings and video quality.

On TCP performance in ATM networks with per-VC early packet discard mechanisms

Both available bit rate (ABR) service and unspecified bit rate (UBR) service with early packet discard (EPD) schemes have been considered for supporting data applications in ATM networks. Since the transmission control protocol (TCP) is perhaps the most widely used transport layer protocol in existing data networks, the performance of TCP over ATM using ABR and UBR services with EPD schemes is of great interest to ATM equipment vendors and service providers. With regard to this interesting issue, we demonstrate in earlier work [1] some simulation results, which show that (1) with UBR service and EPD schemes, TCP suffers significant performance degradation in terms of fairness and requires a relatively large switch buffer even with a small number of active virtual connections over a LAN configuration, and (2) for the same set of network configurations and with ABR service, TCP achieves good performance in terms of fairness and link utilization, and requires relatively small switch buffer. In this paper, we extend our work [1] by studying the performance of TCP over UBR service where EPD schemes are improved by using per-VC accounting and per-VC queueing techniques. In particular, our simulation results show that in a LAN environment, per-VC based EPD schemes can significantly improve the performance of TCP over UBR service in terms of fairness.

Optimal connection admission control in ATM networks

We characterize the achievable performance of ATM networks in terms of the offered traffic, the admissible region, and the revenue measure. We describe how the boundaries of admissible regions with convex complements may be linearized —thus reducing the admissible region — so as to obtain a convenient loss network representation. Asymptotic results for the achievable performance suggest that the potential reduction in revenue is immaterial in high-capacity networks. Numerical experiments confirm that the actual reduction is typically negligible, even in networks of moderate capacity.

Optimal connection admission control in ATM networks

Abstract We characterize the achievable performance of ATM networks in terms of the offered traffic, the admissible region, and the revenue measure. We describe how the boundaries of admissible regions with convex complements may be linearized —thus reducing the admissible region — so as to obtain a convenient loss network representation. Asymptotic results for the achievable performance suggest that the potential reduction in revenue is immaterial in high-capacity networks. Numerical experiments confirm that the actual reduction is typically negligible, even in networks of moderate capacity.

Improving the performance of cell-loss recoveryin ATM networks

A new method for improving the performance of cell-loss recovery using FEC (forward error correction) in ATM networks is proposed. This method provides more correcting coverage than existing methods.

Control and Performance in Packet, Circuit, and ATM Networks [Book Review

Control and Performance in Packet, Circuit, and ATM Networks [Book Review

Cell arrival modeling and related statistical multiplexer performance in ATM networks

A source is assumed to go through independently distributed ON and OFF periods. During an ON period, cells arrive spaced apart in time by a fixed interval. No cells arrive during an OFF period. The probability distribution of the ON and OFF periods are arbitrary. Traffic from a number of such sources is statistically multiplexed. The related statistical multiplexer performance is studied analytically as follows. A statistical multiplexer is modeled as a discrete-time single-server queueing system where the traffic from a new source (conforming to the cell arrival process described above) joins traffic that is already being statistically multiplexed. The aggregated arrival of cells from existing traffic is assumed to follow a two-state Markov modulated cell arrival process. Numerical examples that relate the performance at the statistical multiplexer to the parameters describing the traffic from the new source and the aggregated traffic are presented.

Dimensioning an ATM switch based on a three-stage Clos interconnection network

ATM (asynchronous transfer mode) is a new technique for transmitting voice, data and video. The performance of atm networks will depend on switch structure. Performance analysis of an atm switch based on a three-stage Clos network is presented. In this paper two types of switches are studied: a switch with input queues in the switching elements and a switch with output queues. This study is at the cell level and intends to dimension the switch. First, the traffic is supposed to be uniform, cells arrive on each input according to a geometric arrival process, they are uniformly directed over all the network outputs. An analytic model is proposed for both input and output queues in the switching elements. A study of the saturation throughput is proposed for input buffer switching elements. This work proves the influence of buffer dimensioning on the different stages of the switch. Dissymmetric switching elements are shown to be better than symmetric ones. A model is then designed for nonuniform traffic patterns and output buffers. Two types of non-uniform traffic are presented: single source to single destination (sssd) and multi-hot spots traffic (mhs). Discrete event simulations are used to validate the different models.

Improvements to TCP performance in high-speed ATM networks

Performance of TCP connections in high-speed wide-area ATM networks is of great importance due to the widespread use of te TCP/IP protocol for data transfers and the increasing deployment of ATM networks. ATM technology promises substantial gains by allowing the available link bandwidth to be efficiently used by a mix of audio, video, and data traffic. However, certain features of ATM technology lead to a substantial degradation of TCP connection throughput under congestion conditions. The poor performance of TCP has been observed in a number of recent studies [7] and a number of remedies have been proposed [1, 8], but most of the additional mechanisms proposed to improve TCP performance in ATM networks require substantial complication of the ATM switches