Multi-access Edge Computing (MEC) is a promising technology that provides low-latency processing capabilities. To optimize the network performance in an MEC system, an efficient routing path between a user and its serving MEC host is essential. The network performance is characterized by multiple attributes, including packet-loss probability, latency, and jitter. A user service may require a particular combination of such attributes, complicating the shortest-path computation. This paper introduces Q-Routing for Multi-Objective shortest-path computation (QR-MO), which simultaneously optimizes multiple attributes. We compare the QR-MO’s solutions with the optimal solutions provided by the Multi-objective Dijkstra Algorithm (MDA). The results show the favorable potential of QR-MO. After 100 episodes, QR-MO achieves 100% accuracy in networks with low to moderate average node degrees, regardless of the size, and more than 85% accuracy in networks with high average node degrees.

Multi-access Edge Computing (MEC) is an emerging technology that allows to reduce the service latency and traffic congestion and to enable cloud offloading and context awareness. MEC consists in deploying computing devices, called MEC Hosts (MEHs), close to the user. Given the mobility of the user, several problems rise. The first problem is to select a MEH to run the service requested by the user. Another problem is to select the path to steer the traffic from the user to the selected MEH. The paper jointly addresses these two problems. First, the paper proposes a procedure to create a graph that is able to capture both network-layer and application-layer performance. Then, the proposed graph is used to apply the Multi-objective Dijkstra Algorithm (MDA), a technique used for multi-objective optimization problems, in order to find solutions to the addressed problems by simultaneously considering different performance metrics and constraints. To evaluate the performance of MDA, the paper implements a testbed based on AdvantEDGE and Kubernetes to migrate a VideoLAN application between two MEHs. A controller has been realized to integrate MDA with the 5G-MEC system in the testbed. The results show that MDA is able to perform the migration with a limited impact on the network performance and user experience. The lack of migration would instead lead to a severe reduction of the user experience.

Multi-access Edge Computing (MEC) enhances the capabilities of 5G by enabling the computation closer to the end-user for real-time and context-aware services. One of the main challenges of MEC is the migration of the MEC application in the presence of user mobility. MigraMEC is a hybrid testbed that simulates the network scenario and user mobility and emulates the MEC framework by using AdvantEDGE. Moreover, MigraMEC implements two physical MEC Hosts (MEHs) by using an extended version of Kubernetes (K8s). Finally, the MigraMEC controller interacts with both the emulative and experimental environments to ensure an efficient migration of the MEC application. Based on network information, the MigraMEC controller not only enforces the MEH where the MEC application is running but also the Point of Access (PoA) to which the user is connected. In our demonstration, the MEC application is a video streaming service, and the results highlight the need for multiple MEHs and efficient migration to maintain a high user experience.

This paper addresses two main aspects related to the application of the IEEE 802.11ad technology in an industrial environment, i.e., to guarantee a low latency and reliable data delivery while reducing the number of the deployed Access Points (APs). First, we discuss the parameter settings of the IEEE802.11ad MAC which guarantee a low delay by exploiting the synchronous service periods (SPs) mechanism. Then, we propose a binary linear programming model to enhance the reliability of the system under the Frame Replication and Elimination for Reliability (FRER). The model minimizes the number of deployed APs by taking into account the constraints on the available synchronous SPs. We also propose two heuristics, based on the described mathematical model, in order to efficiently solve the design problem, then compare the computational performance of the proposed approaches. The reported computational results highlight the complementary features of the compared methods and provide useful guidelines about the usage of the proposed approaches.

In this paper, we present a novel method to predict the long-term popularity of user-generated content (UGC). At first, the method clusters the dynamics of UGC popularity into a vocabulary of growth in popularity (sequence) by using a mixture model. Eventually, the method assigns to each sequence a topic model to describe the dynamics of the sequence in a compact way. We then use this topic model to identify similar patterns of growth in popularity of newly observed UGC. The proposed method has two key features: First, it considers the historical dynamics of the UGC popularity, and second it provides long-term popularity prediction. Results on the real dataset of UGC show that the proposed method is flexible, and able to accurately forecast the complete growth in popularity of a given UGC.

The fifth generation (5G) of cellular networks promises to be a major step in the evolution of wireless technology. 5G is planned to be used in a very broad set of application scenarios. These scenarios have strict heterogeneous requirements that will be accomplished by enhancements on the radio access network and a collection of innovative wireless technologies. Softwarization technologies, such as Software‐Defined Networking (SDN) and Network Function Virtualization (NFV), will play a key role in integrating these different technologies. Network slicing emerges as a cost‐efficient solution for the implementation of the diverse 5G requirements and verticals. The 5G radio access and core networks will be based on a SDN/NFV infrastructure, which will be able to orchestrate the resources and control the network in order to efficiently and flexibly and with scalability provide network services. In this paper, we present the up‐to‐date status of the software‐defined 5G radio access and core networks and a broad range of future research challenges on the orchestration and control aspects.

The widespread diffusion of mobile phones and the convergence of more and more services to the mobile devices allow the service providers to collect a huge corpus of information about the behaviour of the users (e.g., location and activity), “transforming” the cellular network into a highly distributed and pervasive sensor network. In this paper, we aim at demonstrating how, by using simple statistical tools, these data can be used to obtain information, often apparently unrelated to the mobile phone usage. To this aim, we have analysed the CDRs collected by Telecom Italia in December 2013 in Milan (Italy) and made available by the “Open Big Data” project, to infer information about the behaviour of foreign people in Milan. Such analysis clearly highlights the potential of applying big data analysis techniques to the mobile providers data.

In LTE and LTE-Advanced systems the rate of requests on the Random Access CHannel (RACH) can be high. Indeed, the Machine Type Communication (MTC) implies to have a high number of devices that need to request radio resources for transmitting small amount of data. Furthermore, reducing the time in which radio resources are allocated to Human Type Communications (HTC) for energy savings purposes, may lead to radio access network overload as well. In this framework, this paper aims at providing a set of guidelines for the resource allocation task in the RACH. In particular, the study investigates the impact of both the backoff indicator scheme and the maximum number of retransmissions on the RACH performance parameters. The rate of RACH requests associated with the HTC traffic is modelled by inferring their statistical properties starting from a dataset acquired in an operational eNodeB. The estimation of the average delay and the average number of maximum retransmissions gives insights on how many preambles should be reserved for HTC in order to meet the target performance, and provides suggestions on the configuration of the backoff indicator.

In the last years, Software Defined Networking has emerged as a promising paradigm to foster network innovation and address the issues coming from the ossification of the TCP/IP architecture. The clean separation between control and data plane, the definition of northbound and southbound interfaces are key features of the Software Defined Networking paradigm. Moreover, a centralised control plane allows network operators to deploy advanced control and management strategies. Effective traffic engineering and resources management policies allow to achieve a better utilisation of network resources and improve end-to-end service performance. This paper deals with the architectural design and experimental validation of a control application that enables differentiated routing for traffic flows belonging to different service classes. The new control application makes routing decisions leveraging on OpenFlow network statistics, i.e., taking advantage of real-time network status information. Moreover, a Deep Packet Inspection module has been developed and integrated in the control application to detect VoIP traffic with Session Initiation Protocol signalling, enforcing this way policies for a differentiated treatment of VoIP traffic. Finally, a functional validation is performed in emulated environment.

In the LTE systems, battery lifetime and network traffic overhead on control plane may be largely affected by the Discontinuous reception (DRX) configuration and the Radio Resource Control (RRC) Inactivity Timer. In this scenario, the paper proposes an analysis aimed at defining how to properly set the RRC Inactivity Timer to achieve a trade-off between energy savings and traffic overhead on the control plane. The analysis is based on an energy consumption model, whose key parameters are inferred directly from passive measurements carried out by monitoring a commercial eNodeB of one of the Italian Mobile Operators. The results suggest that taking into account the network traffic characteristics is possible to find the RRC inactivity timer value that permits to save energy of user's device while the increase of the signalling load is limited.

The paper describes and compares different approaches that can be used to design Network Power Management methods, with the aim of reducing the power consumption of telecommunication networks. The approaches are based on the solution of optimization problems that have, in general, a Mixed Integer NonLinear Programming (MINLP) formulation. Given that the problems are NP-hard, exact methods for finding optimal solutions can be used only for scenarios of limited size. In this framework, the paper proposes a heuristic for finding a suboptimal solution of the Power Aware Routing and Network Design (PARND) problem, which is one of the more general design problems in Network Power Management. The simulation study highlights the capability of the proposed heuristic to obtain solutions near the optimum and to outperform the other approaches in terms of energy savings, while satisfying the constraints of the traffic demands.

Recently, the power consumption of the home/access networks has stimulated several research efforts devoted to the study of new mechanisms to optimize the energy utilization. In particular, most of these works is based on the idea that Ethernet links are mostly underutilized, and is thus aimed at realizing mechanisms able to adapt device consumption to the link utilization. Given the few works presenting an experimental study of the current Ethernet network devices from an energy point of view, this paper aims at presenting an extensive measurements campaign for evaluating the power consumption of two COTS Ethernet NICs. The measurements campaign, carried out following the procedures provided by the ECR Initiative™ and the SNE Energy Star, shows the energy inefficiency of the current NICs. Finally, using the experimental results, the paper presents a qualitative estimation of the energy savings achievable by implementing a well-known energy savings mechanism (i.e., ALR) in the Ethernet NICs.

Many wireless technologies used to build local or personal area networks (WLANs, WPANs) operate into the 2.4 GHz ISM band. Due to the mutual interference, the coexistence of such devices working at the same time in the same area can be troublesome. This paper reports the result of an extensive experimental study on the performance of three popular technologies (ZigBee, Wi-Fi, and Bluetooth), under their mutual disturbance. In addition to assessing the effect of the interference between pairs of technologies, we also analyzed the simultaneous interference among the three systems, a scenario that has never been studied before. Our work partly confirms previous findings, but also reveals some unexpected behaviors, imposing to reconsider some assumptions about the supposed interference-free ZigBee and Bluetooth channels.

Overload is a challenging problem for a SIP server because the built-in overload control mechanism based on generating rejection messages could not prevent the server from collapsing due to congestion. In this scenario, the paper presents an overload mechanism combining a local and a remote solution. The local part of the overload control mechanism is based on the appropriate queueing structure and buffer management of the SIP proxy. The remote overload control mechanism is based on feedback reports provided by the SIP proxy to the upstream neighbors. These reports permit the traffic regulation necessary to avoid the critical condition of overload. The main paper contributions are the design of key components of a remote control mechanism, the proposal of a new approach for dynamic load estimation, and the use of a prediction technique in the remote control loop.

The paper presents a scheduling algorithm for WiMAX systems, which exploits Time-Utility Functions (TUFs) and game theory. The scheduling decision is performed by means of two steps: the intra-class scheduling step and the inter-class scheduling step. In the first one, each user exploits TUFs to choice the packets to transmit according to QoS requirements. In the second one, the scheduler exploits the game theory to select a specific game solution that provides more or less fairness among the users that have to be served. The available physical network resources (i.e. slots) are taken into account as a constraint to the scheduling decision. The proposed scheduling algorithm follows a cross-layer approach that takes into account application requirements by means of TUFs and physical Channel State Information (CSI) of each user. Several game solutions are compared by means of simulation results in terms of user fairness, user throughput, packet delay and packet expiration rate. The TUFs introduction is also evaluated comparing the different applications performance.

As other signaling protocols in the past, also SIP suffers of server overload leading to performance collapse. In this framework, recent Internet drafts propose the improvements of overload control mechanisms already presented in SIP and/or a closed loop system model for overload avoidance. In this framework, the paper presents the system simulator developed extending the network simulator (ns-2) with logical for local overload control. Furthermore, the paper proposes a new queueing discipline obtained combining the simple first in first out (FIFO) service discipline with the priority one. Then the paper presents a simulation analysis, aimed at evaluating the impact on system performance of different queueing structures, service disciplines, and buffer sizes. Simulation results clearly show that the proposed queueing discipline produces good system performance with a low complexity increase. Finally, the simulation results point out the weakness of the 503 service unavailable message mechanism, which does not introduce significant improvement when combined with the proposed solution.

The paper reports an analysis about the convenience of employing multi-protocol label switching (MPLS) to provide mobility in wireless mesh networks (WMNs). In such networks, which are expected to serve a considerable number of mobile users, the efficient support of mobility is a non-trivial issue. The starting point of our work is proxy mobile IPv6 (PMIPv6), a standardised network-based protocol for localised mobility management that has already shown good performance. We analyse and compare PMIPv6 with a recently proposed extension that aims at employing MPLS tunnels in place of IPv6 tunnels. Our contribution is novel in two aspects. First, the analysis focuses on a recent application scenario (the WMN) and accounts for its typical features. Second, we investigate a non-standard use of MPLS (i.e. for micro-mobility management) and provide the first evaluation work of the MPLS tunnel for PMIPv6 technique.

In the last years, broadband satellite networks have emerged as a flexible technology offering high-speed Internet access to large communities of users at relatively low-cost. At the same time, the large widespread of VoIP and Multimedia over IP (MoIP) applications, has pointed out the need of investigating their performance over heterogeneous networks and, more specifically, on wireless and satellite systems not offering Quality of Service (QoS) guarantee. The paper presents the results of an experimental study aimed at analyzing the behaviour of MoIP applications over a two-way satellite system. Starting from the most relevant performance metrics of a satellite network, the paper is focused on the evaluation of the Perceived Quality of Service (PQoS) when VoIP and MoIP applications are deployed over a satellite network. Control and data plane issues that may deteriorate the performance of such applications are highlighted.

The paper presents a measurement campaign carried out on a 2.5 GHz Mobile WiMAX test-bed in a sea port scenario, aimed at evaluating the system performance. The analysis of acquired data suggested the definition of a 2-ray pathloss model, which is able to fit the actual behavior of the observed marine channel. In order to evaluate the effects of the proposed pathloss model on system performance the paper presents a simulation study carried out by means of OPNET simulator. In particular, the simulation study is aimed at comparing the throughput at IP level obtained using different pathloss models implemented in OPNET, with that obtained when the proposed 2-ray model is considered. Further, the throughput at IP level obtained by simulation is compared with the one measured in the actual test-bed. This comparison points out that the WiMAX OPNET model is able to reproduce in most cases the system performance observed during the measurement campaign, when the proposed 2-ray pathloss model is used. However, the simulator is not able to predict the behavior of actual system in all situations. Indeed, in the areas where the pathloss presents peaks, the breakdown of system performance, mainly caused by synchronization problems, is not predicted by the simulator.

We propose a traffic engineering (TE) architecture to supply wireless mesh networks (WMNs) with an efficient support of diverse applications with different quality of service (QoS) requirements. The proposed TE-WMN architecture is based on the MPLS technology. Its main goal is to provide TE capabilities so that a heterogeneous infrastructure, made of wired networks and WMNs, can be built and managed in a seamless manner. In the TE-WMN architecture, the path computation element (PCE) is in charge of finding a path that satisfies the QoS requirements. This operation often requires solving a multi-constrained problem, which is known to be NP-complete. So far many approximated and heuristic solutions have been developed for and applied to wired networks. However, the different features of WMNs make it impractical to reuse those solutions. Hence we have devised two heuristic path computation algorithms (PCAs) with the goal of keeping the complexity very low and yet improving the performance of simple existing algorithms. An extensive set of tests has proved the good performance of the proposed PCAs.

The paper presents a network scenario for multimedia communications during emergency operations in a sea area. The network scenario is composed by a satellite link and a WiMAX system provided by a main naval unit. The WiMAX system permits the communications between the operators on small units and the main naval unit, where there are both local coordinators and the shared satellite link, used for communications between units on the crisis area and the headquarter. The presented network scenario has been experimentally tested in terms of coverage area offered by the WiMAX system, IP throughput and user level quality of service of VoIP applications.

Detecting SPam over Internet telephony (SPIT) and preventing users from it is a raising concern in the research community. At the time of writing some solutions have been already proposed but, to the authors' best knowledge, no extensive study of prevention effectiveness has been published. This paper presents a modular simulator which was built in order to test SPIT prevention systems' effectiveness that is specifically tailored to deal with upcoming SPIT threat and takes into account VoIP and SPIT-specific configurations and parameters. Making use of the developed simulator, the paper also presents a preliminary study on how the single modules can be optimized by means of the simulator and how multiple detection mechanisms can cooperate in order to achieve higher detection accuracy. Moreover the paper provides effectiveness results showing how the modular approach is the most promising for dealing with the SPIT threat.

The recently approved IEEE 802.11e standard improves the support for real-time multimedia applications in Wireless LANs. Yet, to provide some level of guarantee in terms of QoS parameters, it is essential to use an admission control scheme. We have devised one such scheme, which bases the admissibility test on the time occupancy of the medium. The network state is assessed through an analytical model of the EDCA in non-saturation conditions. In the paper, beyond describing the proposed scheme, we also show its effectiveness in the case of voice over IP applications.

In this paper we describe a time-based admission control scheme for multimedia over IP services in wireless LANs based on the IEEE 802.11e standard. We build on an existing work where it was defined a parameter, called network utilization characteristic (NUC), to measure the temporal occupancy of the wireless channel of an IEEE 802.11 network. The work we present is twofold. At first, we extend this parameter to 802.11e systems. A simple Markov chain is used for this purpose. Then we build an admission control scheme based on the so-extended NUC and verify its effectiveness in a practical case: a network with mixed voice and video traffic. Simulations, also with different link qualities, are used to validate the effectiveness of our scheme.

In previous works we have introduced the DTT (Deficit Transmission Time) scheduler, an algorithm to be run at the Access Point to contrast the performance anomaly affecting IEEE 802.11 based networks. DTT has indeed proved to be very effective, as it is able to guarantee proportional fairness and isolation to downlink flows. Yet, due to its centralized nature, it can only put in place a suboptimal solution, as the uplink flows are still uncontrolled We have therefore extended the idea of DTT to a distributed version of the scheduler, called Distributed DTT, or (DT)2. The paper, beyond describing this new algorithm, presents the results of an extensive set of simulations. These show that (DT)2is able to defeat the performance anomaly for uplink flows, thus complementing its ancestor perfectly. A useful side effect is the reduction of the bottleneck effect, that allows more fairness between uplink and downlink directions. We show that these achievements are crucial in supporting the emerging Voice Over WLAN services.

In the paper we introduce and evaluate the performance of the Deficit Transmission Time (DTT) scheduler, a centralized channel aware scheduling algorithm for IEEE 802.11 networks. The scheduler has been designed to face two inconveniences of 802.11: the performance anomaly and the "inter-flow blocking" problem. DTT splits outgoing frames into multiple queues and uses gross transmission times as a measure of the link quality. DTT guarantees each downlink flow an equal time share of the channel, which translates into the desirable properties of proportional fairness and flow isolation. The performance of the scheduler has been measured in terms of the number of VoIP calls that can coexist in the system with an acceptable perceived speech quality. This assessment has been done on the basis of the E-model, an ITU-T standardized computational tool. The results definitely point out the improvement over the plain FIFO policy.

The paper proposes an architecture for a scheduling algorithm to be integrated in IEEE 802.11 access points (AP), able to take into account, besides the transport service class required by the destination user, the channel quality experienced by the destination mobile station (STA). The relevance of this topic is due to the observation that when one or more STAs experience poor radio channel conditions, they increase the time spent to transmit a single packet, due to the retransmission of corrupted frames and the adoption of transmission techniques at a lower bit rate, leading to an inefficient use of the shared medium. These phenomena give, as a consequence, a worsening of the performance of all the STAs sharing the wireless medium, independent of their radio channel conditions. The adoption of a scheduling algorithm able to manage information on channel quality permits these effects to be reduced, not penalizing the STAs experiencing good channel conditions and, as a consequence, their experienced throughput. As a result, only the STAs in bad channel conditions experience a reduction of throughput. A prototype of an AP equipment implementing the proposed architecture is presented: it was obtained by modifying the hierarchical token bucket (HTB) and is referred to as wireless hierarchical token bucket (WHTB). The performance of the presented prototype is evaluated experimentally and compared with those obtained with standard scheduling algorithms, which do not take into account information on channel quality.

The fractal nature of Internet traffic allows extending the application of the nonlinear chaotic system theory to the traffic control in modern telecommunication networks. In particular, the prediction techniques developed for these systems provide teletraffic engineers with a novel powerful tool for designing optimized traffic control algorithms. In this framework, the paper presents the performance evaluation of the Radial Basis Function Predictor (RBFP) in predicting actual traffic data. Predictor parameters are selected automatically by minimizing a suitably defined metric of prediction accuracy. The prediction system is then exploited in a simple resource allocation strategy to test the performance improvement achievable whenever a prediction of the future traffic intensity is available. The results obtained by means of discrete event simulation using actual traffic data are encouraging and stimulate a further-investigation of this approach.

In recent years, the development of a multiservice network, using integrated multiplexing and switching strategies, has converged to an IP-based infrastructure, reducing the relevance of other network solutions, such as a B-ISDN based on ATM. However, to develop an IP-based commercial network, the issues related to quality of service (QoS) support must be addressed. These problems are particularly relevant when a satellite access solution is considered, since the network resources can be limited and expensive. At the same time, demand assignment multiple access (DAMA) protocols permit better exploitation of satellite resources by dynamically allocating system bandwidth in response to user requests. The paper discusses the application to a DAMA satellite access network of different QoS architectures proposed by the IETF and the scientific community. The main novelty of the paper consists in selecting from the alternatives the most suitable solution to be applied to a satellite access network. Furthermore, the advantages and the drawbacks of the proposed architectures are analyzed in detail; the interaction between the control plane of the MAC layer and the resource management at the IP layer is highlighted.

The General Packet Radio Service (GPRS) networks are already implemented by several companies in different countries, however some problems related to the quality of service (QoS) observed by users and the efficient use of radio resources are not yet adequately addressed. In this framework, we propose a scheduling algorithm implemented at MAC layer, named as channel quality aware scheduler (CQAS). The main feature of the CQAS is that the user to serve is established taking into account the estimated channel quality for each of the active traffic flows. The performance of the proposed algorithm are evaluated in terms of goodput experimented by TCP clients, considering a set of concurrent file transfers and independent time varying channels. The comparisons between the CQAS performance and those obtained using a simple work conserving round robin (WCRR) algorithm, highlight the improvements introduced by the proposed algorithm. Moreover, the analysis emphasizes that the appropriate choice of both the channel coding scheme (CS) and the scheduling algorithm is needed in order to increase the radio resource utilization.

The paper deals with the applicability of fractional AutoRegressive Integrated Moving Average (f-ARIMA) processes to traffic modelling. This study is suggested by the ability of f-ARIMA processes in separately capturing both the long range dependence (LRD) and short range dependence (SRD) features of actual traffic. Indeed, the f-ARIMA models permit one to produce synthetic traces with a well-controlled LRD/SRD component ratio. The practical relevance of this feature is tested analytically, by means of discrete event simulations, the queueing performance in several working conditions for two different actual-traffic data sets, respectively related to a LAN-to-LAN interconnection and a videoconference service. In particular, the latter data set, characterised by a strong "low frequency" SRD component, emphasises the improvement on queueing performance evaluation introduced by a low-order f-ARIMA (p,d,0) model with respect to a pure LRD one. On the contrary, the inadequacy of the f-ARIMA model is highlighted when considering the LAN traffic characterised by a quite complex SRD component.

The paper presents a comparison of several traffic models in order to investigate their adequacy to approximate the behaviour of actual traffic in a single server queue under realistic working conditions. Hence, considering queueing systems with finite buffers, models parsimoniously fitting the long range dependence (LRD) property are compared to intrinsically short range dependent models and to flexible ones, capturing both LRD and short range dependence (SRD). The paper highlights an optimistic queueing behaviour evaluated by means of models capturing only LRD property, when realistic buffer sizes are considered and a strong SRD correlation component is present. The simulation results point out that the circulant modulated Poisson processes (CMPP) and fractional autoregressive integrated moving average (p,d,0) (f-ARIMA(p,d,0)) are suitable models to estimate the performance of the queueing system under heavy load conditions. On the contrary, when the system works under low-medium load conditions, the relevance of the marginal distribution to queueing performance and the inaccuracy of the CMPP model on fitting this statistic in the case of actual traffic data lead to a reduction of the accuracy of this model on system performance evaluation.

The paper presents joint measurements of IP and ATM traffic over an MPOA based campus network. The search for parsimonious realistic modeling of heterogeneous aggregated traffic has led to the generalization of on/off modeling schemes. Even a single on/off pattern with Pareto-geometric distributions of the sojourn times in each state determines a hyperbolic decay of the autocovariance function corresponding to long range dependence (LRIB). Hence, adequate on/off models can fit real traces corresponding to the multiplexing of several heterogeneous connections. In the paper, the on/off behavior of the traffic is evidenced at the ATM level. The relevant feature of the traces is that either the on and the off sojourn times could be well approximated by a light tailed distribution. The observed LRD behavior is due to the presence of correlation in the sequence of on (as well as off) periods lengths. In order to confirm this hypothesis, different synthetic traces were considered, verifying the LRD behavior by means of wavelet analysis. Implications of such state correlations on queueing behavior are then compared by means of discrete event simulations.

The paper presents the analysis of the applicability of /spl alpha/-stable processes in traffic modelling. This study is suggested by the goodness of /spl alpha/-stable processes in capturing not only the long range dependence (LRD) of actual traffic, but also the heavy tailness of its marginal distribution. The relevance of this property is proved by means of discrete event simulations carried out considering two different data traffic sets, respectively related to a LAN-to-LAN interconnection and entertainment video service. Errors in the estimation of Hurst parameter and in the evaluation of queueing behaviour are highlighted either analytically and empirically by simulations. In particular the queueing simulations have emphasised the improvements in the performance forecasting introduced by the higher flexibility of /spl alpha/-stable model with respect to the widely used fractional Brownian motion (FBM).

Preventive actions have to be used to avoid congestion in ATM networks. These actions are represented by call admission control (CAC) and usage parameter control functions (UPC). Two UPC algorithms are compared and an enhancement of the leaky bucket mechanism is presented. The comparison is based on the results of several trace driven simulations. The simulations, realised on a CAMAD tool, are driven by MPEG1 video traces as input traffic. The effectiveness of the proposed algorithm has been evaluated in terms of response time and transparency. These performance indexes have been obtained considering the number of non-conforming cells and the mean value of the conforming cells path.