Asynchronous Transfer Mode Networks Research Articles

Mobility management and control in intelligent wireless ATM networks

This paper shows how the Asynchronous Transfer Mode (ATM) signaling and the Intelligent Network (IN) concept can be exploited to support mobility in an ATM-based network with wireless access parts and mobile users. The proposed architecture exploits the enhanced service control processing features offered by the IN technology to support location management. The access signaling protocol structure is based on the principles of separation between call and bearer channel control, employed in fixed broadband access networks. The design objective is to minimize the changes required to the wired network signaling, by taking advantage of the well-developed capability sets. This allows the easy introduction of the wireless ATM technology (W-ATM) into the real world. It is shown that the proposed signaling protocol model provides cost-effective implementations without degrading the agreed Quality of Service (QoS) and the system's performance. A comparative signaling performance evaluation is carried-out to demonstrate the impact of the proposed signaling protocol architecture onto various performance measures and to quantify the relative gains. The obtained results can be used for network design purposes in a large-scale private installation supporting many users. The signaling protocol architecture aims for private W-ATM networks, but can be readily extended to fulfill the signaling requirements of public environment broadband wireless systems.

Design of a new globally stable explicit rate controller for ABR service with saturation

In this paper, we consider the closed-loop rate-based flow control for available bit rate (ABR) service in asynchronous transfer mode (ATM) networks, where the ABR sources adjust their transmission rates in response to feedback explicit rates (ER) from the network switches. The feedback ER may be saturated due to the peak cell rate (PCR) and the minimum cell rate (MCR). The buffer occupancy state of the network switch can also be saturated due to the buffer occupancy. To solve saturation nonlinearity problem and analyze the stability globally, a new ER controller is designed, which is composed of a nonlinear controller and a linear controller. The nonlinear controller is employed to bring buffer occupancy state inside the buffer saturation limits and ensure ER value between PCR and MCR. The linear controller is used to ensure that the buffer occupancy state converges to the desired buffer state. Finally, we demonstrate that good transient and steady-state performances can be achieved through a numerical example.

Average waiting time of customers in a priority M/D/k queue with finite buffers

Analysis of priority multiserver queues is known to be a difficult problem. In this paper, a priority M/D/k queue with finite buffers is analyzed and an approximate closed-form expression for the average waiting time of customers belonging to different priority classes is obtained. The key assumption is the presence of heavy traffic in the network leading to loss of customers from the service stations. Several interesting numerical results are reported that show the interplay between arrival and service rate of customers, capacity of the buffer, proportion of traffic belonging to each class and probability of loss as experienced by incoming customers. Scope and purpose Priority queues with finite buffers are used to model various types of telecommunications and manufacturing situations. These queues are specially useful for modeling high-speed asynchronous transfer mode (ATM) networks that are subject to loss due to overfilling of the buffers. In general, it is difficult to obtain closed-form solutions of the various performance measures for these queues. Analysis of such queues with the deterministic service discipline can help provide useful guidelines for designers and developers of telecommunication and manufacturing networks.

Threshold-based congestion control scheme for ABR services in ATM networks

In this paper, an effective flow control scheme, modified explicit rate indication for congestion avoidance (MERICA), is proposed to adaptively release congestion and enhance throughput for available bit rate (ABR) services in asynchronous transfer mode (ATM) networks. The proposed scheme mainly employs thresholds to determine the traffic status. Whenever the traffic status is changed, the switch will immediately inform the source of the new allowed data rate through the resource management (RM) cell in order to regulate the ABR traffic. For efficiently deriving thresholds, a Markov chain model is developed to precisely describe the behavior of the traffic pattern in ATM networks. Moreover, an algorithm is proposed to efficiently solve the thresholds from the Markov chain model under the time complexity of O( N). Finally, a simulation model is presented to investigate the performance. From the simulation results, the proposed scheme can obtain lower loss rate and higher utilization than other methods.

Balanced packet discard for improving TCP performance in ATM networks

TCP suffers from low performance over asynchronous transfer mode (ATM) networks. This is mainly because during phases of congestion, ATM drops cells without taking into account the effect this has on the upper layer protocols. Two main algorithms, called partial packet discard (PPD) and early packet discard (EPD), were proposed in the past for improving TCP performance. However, they address one aspect of the problem that has only small effect on the final performance. In this paper we propose an enhanced method for packet discard, called balanced packet discard (BPD) that improves TCP performance dramatically on congested networks and guarantees fairness among multiple connections. We will show that BPD increases TCP throughput by more than 25% compared to EPD/PPD.

A method to improve the robustness of MPEG video applications over wireless networks

It is important that applications deployed in wireless networks be robust enough to accommodate different kinds of data losses due to link errors, connection re-routing, and network congestion. A scheme to improve the robustness of MPEG based video applications is proposed. Under this scheme, the packet size at the sender is optimized to the MPEG system layer unit size to enable fast recovery of the time stamps. The receiver buffers the data packets for re-playing during packet losses, preserves useful time stamps for synchronisation, and re-synchronises the decoder when packet loss occurs. This involves no feedback and results in faster recovery of critical timing information for video decoding. The proposed method has been implemented on a video application based on MPEG-I over an Asynchronous Transfer Mode (ATM) network. The experiments show that the proposed technique is very effective when there is deterministic/random packet losses with burst size less than 21. The method is equally applicable to video applications based on MPEG-II program stream and, to wireless Internet.

Comparative study of two flow control mechanisms in high speed networks

Considerable protocol development efforts in recent ATM (Asynchronous Transfer Mode) Forum activities have been focused on the traffic management of available bit rate (ABR) service. It has been shown that ABR service enables persistent, greedy data sources to efficiently utilize ATM network resources with the help of a rate-based flow control mechanism. ATM Forum Traffic Management Specification Version 4.0 document gives a complete description of the end system behavior of the flow control mechanism, but it leaves the details of the switch behavior to be vendor-implementation dependent. For the sake of compatibility and interoperation among flow control mechanisms implemented by vendors, two rate-based mechanisms EPRCA (Enhanced Proportional Rate Control Algorithm) and ERICA (Explicit Rate Indication for Congestion Avoidance) have been recommended in the specification. In this paper, the mechanisms are studied and their performance is analyzed and compared with a material network. Simulation shows that ERICA is significantly better than EPRCA in the performance of steady state and instantaneous state of source end system ACR (Allowed Cell Rate) and buffer queue of bottleneck switch.

Computational intelligence in management of ATM networks

Designing effective control strategies for asynchronous transfer mode (ATM) networks is known to be difficult because of the complexity of the structure of networks, nature of the services supported, and variety of dynamic parameters involved. Additionally, the uncertainties involved in identification of the network parameters cause analytical modeling of ATM networks to be almost impossible. This renders the application of classical control system design methods (which rely on the availability of these models) to the problem even harder. Consequently, a number of researchers are looking at alternative non-analytical control system design and modeling techniques that have the ability to cope with these difficulties to devise effective, robust ATM network management schemes. Those schemes employ artificial neural networks, fuzzy systems and design methods based on evolutionary computation. In this survey, the current state of ATM network management research employing these techniques as reported in the technical literature is summarized. The salient features of the methods employed are reviewed.

Studies of ATM for ATLAS high-level triggers

This paper presents some of the conclusions of our studies on asynchronous transfer mode (ATM) and fast Ethernet in the ATLAS level-2 trigger pilot project. We describe the general concept and principles of our data-collection and event-building scheme that could be transposed to various experiments in high-energy and nuclear physics. To validate the approach in view of ATLAS high-level triggers, we assembled a testbed composed of up to 48 computers linked by a 7.5-Gbit/s ATM switch. This modular switch is used as a single entity or is split into several smaller interconnected switches. This allows study of how to construct a large network from smaller units. Alternatively, the ATM network can be replaced by fast Ethernet. We detail the operation of the system and present series of performance measurements made with event-building traffic pattern. We extrapolate these results to show how today's commercial networking components could be used to build a 1000-port network adequate for ATLAS needs. Lastly, we list the benefits and the limits of ATM for our application and discuss an alternative approach based on fast/gigabit Ethernet.

A transceiver circuit for ATM networks

This paper presents a transceiver digital circuit. The circuit is responsible for the emission of packets to the asynchronous transfer mode (ATM) network as well as for the manipulation of received ATM packets belonging to virtual connections. It has been designed to support data communication services. The circuit, which can be used in terminals or in interworking units and switches, implements basic functions of the lower layers of the ATM protocol reference model. The transmission functionality includes cell buffering, header error control, cell assembling, rate coupling and information insertion. The receiver realizes information extraction, rate decoupling, cell buffering, header error detection and correction, connection identity fields extraction and identification, cell disassembling and classification, and idle cell discarding functions. The circuit has been implemented on applications specific integrated circuit (ASIC) chips.

A new per-VC scheduling scheme in ATM networks: two-phased weighted fair queuing

The asynchronous transfer mode networks should support widely different characteristics of services with different quality of service requirements, and should achieve a fair use of the available bandwidth. This paper proposes a new per-VC scheduling algorithm not only to improve the performance of cell loss probability (CLP) and cell delay variation (CDV) but also to maintain the fair utilization of available bandwidth. The two-phased weighted fair queuing (TWFQ) scheme makes use of the cell inter-arrival time of each connection for determining the cell service order among connections, which contributes to get a small CDV. To achieve low CLP, the TWFQ scheme allows the connections, which are suffering from more bursty input traffic, to send the cell in advance by using two scheduling phases. The simulation results show that TWFQ scheme provides better performance than SCFQ and WRR in terms of CDV and CLP, and also performs as well on the criteria of mean cell delay and bandwidth fairness as those schemes.

An integrated framework for traffic control in ATM networks based on soft-computing techniques

Abstract In this paper we assess the application of artificial intelligence techniques to the complex problem of traffic control in Asynchronous Transfer Mode (ATM) networks. The paper deals with the close link between Call Admission Control (CAC) and Usage Parameter Control (UPC) and proposes a simulation-based analysis to demonstrate how inefficiency on the part of policing affects bandwidth allocation. To take this into account, the paper proposes a framework for traffic control in which the CAC and policing functions are both based on artificial intelligence techniques, i.e., neural networks and fuzzy logic. A measurement-based CAC mechanism is then proposed and implemented by means of neural networks trained in such a way as to take into account the real behaviour of the policer. As the results obtained show, this allows us to implement traffic management strategies that can improve the exploitation of network resources.

Queueing system with multiple delay and loss priorities for ATM networks

Abstract The asynchronous transfer mode (ATM) has been widely accepted as an effective technique to transport various traffics such as voice, data and video in broadband integrated services digital networks (B-ISDN). To utilize the network resources efficiently and to provide the required quality of service (QoS) of each traffic, a proper priority control is necessary. This paper investigates a priority queueing model with four types of traffics, classified according to the delay and loss sensitivity. A head-of-line (HOL) scheme for cell delay control and a push-out scheme for cell loss control are adopted. Some computational procedures for loss probabilities and waiting times are developed. Several numerical examples are also given.

A novel FLC-based approach for ATM traffic control

This paper presents a fuzzy logic controller (FLC) approach to control traffic sources in asynchronous transfer mode (ATM) networks. The proposed traffic controller consists of two main parts: fuzzy connection admission controller (FCAC) and intelligent usage parameter controller (IUPC). The FCAC, for all incoming connections, estimates the required bandwidth and then decides whether to accept or reject them. Simulation results show that the proposed FCAC increases the accuracy of required capacity estimation in comparison with other fuzzy and non-fuzzy bandwidth estimation methods. The IUPC is responsible for monitoring and regulating the input traffic stream after the FCAC accepts the connection. This is achieved by employing a fuzzy controller with the main goal of dynamically tuning the leaky rate based on the state of the traffic source. The necessary control actions are taken based on accurate estimation of the mean cell rate in real time. To exploit the benefits of statistical multiplexing gain, the IUPC in our FLC approach uses a network congestion internal feedback to make a decision as to whether to discard or tag the violating cells. To highlight the merit of the proposed method, different experimental simulations are performed. It is observed that the proposed FLC traffic controller not only has a high statistical multiplexing gain but also can protect quality of services (QoS) of well behaving connections much better than traditional traffic controllers.

Comparison of network protocol and architecture for distributed virtual simulation environment

In any distributed virtual simulation environment, the underlying network architecture and its protocols play an important part in its performance. This paper describes the different underlying protocols used in the support of the RTI implementation in the Federated Simulations Development Kit (FDK). The communication FM and MCAST modules were modified to support different protocols. The performance of two different protocols: TCP and a new Lightweight Reliable Multicast, called Pseudo Reliable Multicast Protocol (PRMP), running on top of two different network architectures Ethernet and Asynchronous Transfer Mode (ATM) were compared. The latter protocol was developed specifically to support the distributed virtual simulation environment. Furthermore, in the case of the ATM network architecture, the use of native ATM-API was also implemented and its performance compared with the other protocols. The benchmarks used to compare their performance are Latency and Time Advance Request Benchmark. The results show that PRMP outperforms the other protocol techniques when the number of subscribers are large and when the bandwidth is limited. But it has some additional latency overhead, due to additional processing required to provide the reliability needed by the sender and receivers. Comparing the network architecture, the benchmark performance of the above protocols operating on top of 100BaseT switch network performs much better than over ATM network, although the transmission speed is much higher in the case of the latter.

How ATM Networks Meet Professional Broadcast Demands

Through the combination of digital TV and digital networking technologies, the transport of professional broadcast services is undergoing a tremendous evolution. After a move from analog to digital, specialized leased lines are being replaced progressively by powerful general purpose asynchronous transfer mode (ATM)-based networks. The most critical issue for the adoption of this new technology by the broadcast industry is the transport of live realtime broadcast services, for which the most serious constraints appear. The level of performance that can be expected for this application is a key point for the end-user broadcaster. After reviewing various elements of the ATM technology, this paper focuses on performance aspects: the mechanisms put in place, leading to commitments by both the end-user broadcaster and the network operator to a given level of performance are explained; practical performance results are given; and examples of large-scale deployments are described.

Performance models of handover protocols and buffering policies in mobile wireless ATM networks

Due to the connection-oriented nature of the asynchronous transfer mode (ATM), one of the challenges in mobile wireless ATM (WATM) systems is the management of terminal handovers. When ATM connections are reestablished to follow terminals moving between areas covered by distinct base stations, seamless handover protocols are necessary to guarantee that ATM cells are delivered to terminals in the correct order, with cell loss rate and delay that satisfy the contracted quality of service (QoS). A promising approach to meet QoS requirements is based on the use of handover buffers at the (destination) base station, where transmitted cells are stored while the connection is being reestablished. Up to date, only simulation and experimental results are available to determine the performance of such protocols and buffering schemes. This paper presents the first attempt to develop an analytical modeling approach to estimate the performance of handover protocols making use of handover buffers at the base station. By incorporating several approximations, the proposed models allow designers to simultaneously take into account numerous system parameters, including handover buffer size, sustainable and peak cell rates of the ATM connection, terminal offered load, and time needed to reestablish the ATM connection. Analytical performance predictions are shown to closely match results of detailed simulation experiments, thus demonstrating the suitability of the proposed modeling framework for the selection of the most adequate solution to handle handover and provide the QoS required by end users.

Design and analysis of QoS supported frequent handover schemes in microcellular ATM networks

Wireless information networks need to employ small radio cells to support large user populations. However, this will impose extra burden on network traffic control as a result of frequent handover behavior. Existing approaches to support a high handover rate still have cell loss and cell out-of-sequence penalty while the handover is in progress. This paper proposes a novel handover protocol that can avoid cell loss and guarantee cell sequence. It can enhance the performance of a microcellular asynchronous transfer mode network. By multicasting cells to a new base station before handover, our scheme can avoid cell loss and support a nonoverlapping microcell environment as well. The multicast of signaling messages during handover is to coordinate the cell transmission order between the old base station and the new base station to guarantee cell sequence. A formal representation of the handover protocol using finite-state diagrams has been developed to specify and verify the protocol. To guarantee quality of service, we present a hierarchical wireless call admission control to limit the number of in-progress connections and to prevent radio channel congestion. Mathematical models have been developed to analyze two quality-of-service parameters: handover dropping probability and forced termination probability. Experimental results show that our hierarchical wireless call admission control can effectively lower the handover dropping probability and the forced termination probability in comparison with the single-layer wireless call admission control.

Interoperability of EFCI and ERICA ATM switches for ABR services with VS/VD enhancements

To improve network bandwidth utilization, the asynchronous transfer mode (ATM) forum has standardized available bit rate (ABR) service which requires a number of parameters to be negotiated during connection setup. MCR is the minimum cell rate guaranteed by the network and can be used to provide an acceptable quality of service for applications. In this study, explicit forward congestion indication (EFCI) and explicit rate indication for congestion avoidance (ERICA) switches were adopted in a current transitional ATM network. First, we transfer traffic with ABR service to realize the interoperability of EFCI and ERICA switches. Second, we implemented the virtual source/virtual destination (VS/VD) feature into a homo or heterogeneous EFCI and ERICA switch environment in order to observe the performance. From the simulation results, a smaller queue length was obtained after the VS/VD was introduced into the EFCI and ERICA switches. The high link data transfer utilization with ABR service was also obtained.

Improving image and video transmission quality over ATM with foveal prioritization and priority dithering

Several characteristics of the asynchronous transfer mode (ATM) protocol are making it increasingly popular with designers of networked multimedia systems. However, the main drawback to ATM-based switching is the possibility of information loss with congestion. In this paper, we address this issue; we demonstrate that with intelligent, fovea-driven priority assignment of image data, we can reduce the negative impact of information loss over ATM networks. ATM standards allow a single bit to indicate high or low packet priority. To reduce the effect of this restriction we introduce the concept of priority dithering. Network multimedia multicast scenarios over heterogeneous link capacities where foveal prioritization would be of benefit are described. Network simulation results of this method are included which demonstrate the advantages of priority dithered foveal prioritization over traditional methods.