Per-source mean cell delay and mean buffer contents in ATM queues

Most performance studies of ATM cell buffers so far have been limited to global performance characteristics such as the total mean buffer contents and the global mean cell delay. The authors present an analytical technique which allows the derivation of performance measures for single sources     

ATM cell delay and loss for best-effort TCP in the presence ofisochronous traffic

This paper reports the findings of a simulation study of the queueing behavior of “best-effort” traffic in the presence of constant bit-rate and variable bit-rate isochronous traffic. In this study, best-effort traffic refers to ATM cells that support communications between host end systems executing various applications and exchanging information using TCP/IP. The performance measures considered are TCP cell loss, TCP packet loss, mean cell queueing delay, and mean cell queue length. Our simulation results show that, under certain conditions, best-effort TCP traffic may experience as much as 2% cell loss. Our results also show that the probability of cell and packet loss decreases logarithmically with increased buffer size     

On multimedia networks: self-similar traffic and networkperformance

The main objective in telecommunications network engineering is to have as many happy users as possible. In other words, the network engineer has to resolve the trade-off between capacity and QoS requirements. Accurate modeling of the offered traffic load is the first step in optimizing resource allocation algorithms such that provision of services complies with the QoS constraints while maintaining maximum capacity. As broadband multimedia services became popular, they necessitated new traffic models with self-similar characteristics. We present a survey of the self-similarity phenomenon observed in multimedia traffic and its implications on network performance. Our current research aims to fill the gap between this new traffic model and network engineering. An immediate consequence of this study is the demonstration of the limitations or validity of conventional resource allocation methods in the presence of self-similar traffic     

On optical burst switching and self-similar traffic

In this letter we consider burst switching for very high speed routing in the next generation Internet backbone. In this scenario, Internet protocol (IP) packets to a given destination are collected in bursts at the network edges. We propose a burst assembly mechanism that can reduce the traffic autocorrelation or degree of self-similarity, and at the same time keep the delay due to burst formation limited at the network edges     

Evaluation and comparison of cell loss and delay models for ATM multiplexers

Among several models that are available to represent the aggregate cell flow generated by on–off sources at an ATM multiplexer (either at an access or a switching node), the Interrupted Bernoulli Process (IBP) is characterized by particular simplicity and analytical tractability. The superposition of sources individually modeled as an IBP, whose cells enter a common buffer, is considered in this paper. The main goal is to compute approximations of two basic Quality of Service (QoS) indicators, namely, cell loss rate, whose analytical computation has been already presented in previous works, and the rate of cells exceeding a specified delay, whose presentation constitutes the theoretical novelty of the paper. Analytical expressions of these two quantities are given for homogeneous sources, i.e., possessing the same statistical parameters and QoS requirements. The analytical formulation is carefully evaluated by comparing the results obtained with others presented in the literature and with simulation results; in the latter, the actual cell arrival process is generated by means of a Markov Modulated Deterministic Process (MMDP) model of the on–off sources. Several comparisons are performed for different offered loads and by varying the buffer length, which show the effectiveness and the limits of the technique under investigation.     

A traffic measurement method and its application for cell lossprobability estimation in ATM networks

Focuses on how to determine a set of parameters describing cell arrival stream characteristics and how to evaluate the accuracy of these measurements. Since a cell arrival stream is both correlated and bursty, the autocorrelation characteristics between the number of arriving cells in two adjacent intervals are analyzed, and then the time interval is determined for which the autocorrelation may be neglected. It is also shown that this set of parameters can represent the first and approximately second moment statistics during any interval. A method of estimating cell loss probability through the use of a queuing model that has an input process is presented. The input process is determined from the set of parameters that describe the characteristics of the source. In order to verify the accuracy, a brief simulation study is carried out     

Bandwidth-dependent scheduling algorithm to limit cell delayvariation for CBR traffic in ATM networks

A multiplexing control scheme is proposed for limiting the cell delay variation (CDV) caused by multiplexing of constant bit rate (CBR) traffic in asynchronous transfer mode (ATM) networks. The control scheme is based on a bandwidth-dependent scheduling algorithm. The limitation of the CDV is proved     

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     

Using fuzzy logic in ATM source traffic control: lessons andperspectives

Due to its capacity to capture human expertise and to formalize approximate reasoning processes, fuzzy logic can be a good answer to the many challenges of congestion control in ATM networks. The authors deal with the application of fuzzy logic to problems of usage parameter control and propose a simple mechanism which, avoiding complex mathematical calculations, guarantees low response times while remaining effective. The flexibility of the fuzzy control proposed is discussed with respect to the probability of facing various types of traffic sources, ranging from bursty to MPEG video     

Survey of traffic control schemes and protocols in ATM networks

The authors survey a number of important research topics in ATM (asynchronous transfer mode) networks. The topics covered include mathematical modeling of various types of traffic sources, congestion-control and error-control schemes for ATM networks, and priority schemes to support multiple classes of traffic. Standard activity for ATM networks and future research problems in ATM are also presented. It is shown that the cell-arrival process for data sources can be modeled by a simple Poisson process. However, voice sources or video sources require more complex processes because of the correlation among cell arrivals. Due to the effects of high-speed channels, preventive control is more effective in ATM networks than reactive control. Due to the use of optical fibers in ATM networks, the channel error rate is very small. The effects of propagation delay and processing time become significant in such high-speed networks. These fundamental changes trigger the necessity to reexamine the error-control schemes used in existing networks. Due to the diversity of service and performance requirements, the notion of multiple traffic classes is required, and separate control mechanisms should be used according to the traffic classes. The priority scheme is shown to be an effective method to support multiple classes of traffic     

An efficient method for computing cell loss probability for heterogeneous bursty traffic in ATM networks

In this paper, we present an approximation for the probability of cell loss of heterogeneous bursty traffic in broadband integrated packet networks based on the asynchronous transfer mode. The sources considered here alternate between active and silent periods and are characterized by their peak and average transmission rates. The cell loss probability is obtained by considering only the number of active sources at a given time and computing the amount of traffic that exceeds the link capacity. Since the amount of buffered excess traffic is not considered in this computation, this approximation is actually an upper bound of the cell loss probability. The numerical efficiency of this bound enables it to be used as a measure based on which robust and simple resource allocation strategies can be developed for bursty sources. Comparison of this bound with the simulation results has shown that the bound is close to the actual loss probabilities especially for large burst lengths and high utilizations.     

Flow control schemes and delay/loss tradeoff in ATM networks

Performance and flow control mechanisms, which represent ATM (asynchronous transfer mode) flexibility, are discussed. To control performance, delay- and/or loss-sensitive service classes, and two mechanisms to realize these classes, are proposed. It is shown that it is possible to have better performance than with other mechanisms, such as no-class distinction or simple priority methods. It is further suggested that this performance controllability results in the provision of multiple logical services, including quasi-STM (synchronous transfer mode; compatible with circuit switching), by an ATM network. ATM flow control is based on a call-oriented resource allocation mechanism similar to circuit switching. The concepts of call/line bit rate ratio and multiplexing degree are seen to be significant for efficient use of resources. When the network handles calls with large call/line bit rate ratios, user-specified flow control parameters at the call setup phase are important for resource assignment. The definition of two types of maximum throughput of each call and its usage for resource management are proposed     

On the Cramer- Rao bound for time delay and Doppler estimation (Corresp.)

Using a theorem due to Whittle, simple derivations of the Cramer-Rao lower bound are presented for some delay estimation problems related to a single source, multiple sources, and multipath. The problem of Doppler estimation is briefly discussed.     

Neural networks in B-ISDN flow control: ATM traffic prediction ornetwork modeling?

The authors discuss a technique that offers the combination of shared bandwidth and rejection rate parameters, together with the quality of service predicted by neural networks in a novel strategy for connection admission control and call routing     

A new approach for allocating buffers and bandwidth toheterogeneous, regulated traffic in an ATM node

A new approach to determining the admissibility of variable bit rate (VBR) traffic in buffered digital networks is developed. In this approach all traffic presented to the network is assumed to have been subjected to leaky-bucket regulation, and extremal, periodic, on-off regulated traffic is considered; the analysis is based on fluid models. Each regulated traffic stream is allocated bandwidth and buffer resources which are independent of other traffic. Bandwidth and buffer allocations are traded off in a manner optimal for an adversarial situation involving minimal knowledge of other traffic. This leads to a single-resource statistical-multiplexing problem which is solved using techniques previously used for unbuffered traffic. VBR traffic is found to be divisible into two classes, one for which statistical multiplexing is effective and one for which statistical multiplexing is ineffective in the sense that accepting small losses provides no advantage over lossless performance. The boundary of the set of admissible traffic sources is examined, and is found to be sufficiently linear that an effective bandwidth can be meaningfully assigned to each VBR source, so long as only statistically-multiplexable sources are considered, or only nonstatistically-multiplexable sources are considered. If these two types of sources are intermixed, then nonlinear interactions occur and fewer sources can be admitted than a linear theory would predict. A qualitative characterization of the nonlinearities is presented. The complete analysis involves conservative approximations; however, admission decisions based on this work are expected to be less overly conservative than decisions based on alternative approaches     

Scalable architectures for integrated traffic shaping and linkscheduling in high-speed ATM switches

Emerging broad-band switches must accommodate the diverse traffic parameters and quality-of-service requirements of voice, data, and video applications. End-to-end performance guarantees depend on connections complying with traffic contracts as their cells travel through the network. This paper presents a leaky-bucket shaper architecture that scales to a large number of connections with diverse burstiness and bandwidth parameters. In contrast to existing designs, the proposed architecture arbitrates fairly between connections with conforming cells by carefully integrating leaky-bucket traffic shaping with rate-based scheduling algorithms. Through a careful combination of per-connection queueing and approximate sorting, the shaper performs a small, bounded number of operations in response to each arrival and departure, independent of the number of connections and cells. When the shaper must handle a wide range of rate parameters, a hierarchical arbitration scheme can reduce the implementation overheads and further limit interference between competing connections. Through simulation experiments, we demonstrate that the architecture limits cell-shaping delay and traffic distortions, even in periods of heavy congestion. The efficient combination of traffic shaping and link scheduling results in an effective architecture for managing buffer and bandwidth resources in large, high-speed ATM switches     

基于市场拍卖模型的ATM网络ABR业务控制

本文提出一种分布式的、基于用户竞价模型的ＡＴＭ网络ＡＢＲ业务控制机制,可为用户提供在业务传输中没价格与不同服务质量等级之间的协商。在此欺压耻我们定义了新的资源利用公平性准则。它是最大一最小准则的扩充,本文方法所用的控制和计旨易于实现,并且遵循ＡＴＭ论坛提出的ＡＢＲ业务明确位率反馈控制规范,因而此方法ＡＢＲ业务的计旨几分布式管理相集成提供了一条新思路。     

Scheduling reserved traffic in input-queued switches: new delay bounds via probabilistic techniques

We consider the problem of providing delay bounds to reserved traffic in high-speed input-queued switches. We assume that the matrix of bandwidth demands is known, and we use the now standard approach of decomposing this matrix into a convex combination of permutation matrices. Our problem, therefore, reduces to the problem of constructing a schedule for these permutation matrices. We derive delay bounds for four algorithms that are based on probabilistic techniques. For each algorithm, we first place tokens randomly in continuous time for each permutation matrix. If the nth token that appears corresponds to permutation matrix M/sub k/, then we schedule matrix M/sub k/ in the nth time slot. The algorithms differ in how the random token processes are defined. For two of the algorithms, we are able to perform a derandomization so as to obtain deterministic schedules. We show through numerical computation that in many situations the resulting delay bounds are smaller than the previously best-known delay bounds of Chang et al. (see Proc. IEEE IWQoS, London, U.K., 1999 and Proc. IEEE INFOCOM, Tel-Aviv, Israel, Mar 2000).     

Integrated cell and frame switching in ATM networks

Based on the per-VC queueing architecture, we propose a new technology to integrate cell and frame switching in asynchronous transfer mode (ATM) networks. We demonstrate that we can switch both fixed-length cells and variable-length frames inside the same switch at the same time. The insight is to recognize that we can store not only fixed-length cells, but also variable-length frames in each VC queue. The seamless integration of frame switching with cell switching will have a potential of merging frame relay with ATM