Maurizio Mongelli

On-line bandwidth control for quality of service mapping over satellite independent service access points

In the broadband satellite multimedia (BSM) architecture, developed by the European Telecommunications Standardizatlon Institute (ETSI), the physical layers are isolated from the rest by a satellite independent-service access point (SI-SAP). For technological reasons, satellite independent (SI) traffic accesses, requiring different QoS guarantees, must be aggregated together within the satellite dependent (SD) core and may change encapsulation format. Moreover, SD layers must assure proper fading countermeasures to face satellite channel radiation. In this work, we investigate a novel control algorithm to tackle the envisaged problems. Simulation results update the proposed approach

Vertical QoS mapping over wireless interfaces

This article focuses on the problem of quality of service mapping between layers in a cascade. Protocol stacks in telecommunications networks are composed of functional layers. QoS provision depends on the performance achieved at each layer and is based on functions performed at layer interfaces. In practice, QoS derives from reliable physical and link layers that can offer specific transport services to upper network layers. The data flows (or bundles of flows) generated by the upper layers (e.g., the network layers) are forwarded down to a physical interface that transports the information along a channel that provides, if possible, the expected QoS to the upper layers. The action is called vertical QoS mapping and poses many challenges for a communication scientist, in particular if it is applied to wireless interfaces. This article states the definition of vertical QoS mapping, proposes a formal separation between technology-dependent and technology-independent layers, models each functional layer as a battery of buffers, generalizes the relation between layers through a chain of buffers in a cascade, formalizes the theoretical problems of vertical QoS mapping, and suggests possible solutions that use dynamic bandwidth allocation schemes.

An on-line intrusion detection approach to identify low-rate DoS attacks

This paper addresses the problem of detection of “Slow” Denial of Service attacks. The problem is particularly challenging in virtue of the reduced amount of bandwidth generated by the attacks. A novel detection method is presented, which analyzes specific spectral features of traffic over small time horizons. No packet inspection is required. Extrapolated data refer to real traffic traces, elaborated over the Local Area Network of our Institute. Different kinds of attacks have been considered as well. The results show how the proposed method is reliable and applicable in many other contexts.

A proposal of new price-based Call Admission Control rules for Guaranteed Performance services multiplexed with Best Effort traffic

Pricing for the use of telecommunication services is an issue widely treated in the literature. In the last years it has received a growing attention in order to establish various fairness criteria in the bandwidth allocation for each type of traffic class. A number of pricing models have been proposed and analyzed in the context of Quality of Service (QoS) guaranteed networks (e.g. ATM, IP Integrated Services, IP Differentiated Services) and more recently, also for Best Effort (BE) environments. In the context of QoS networks the pricing scheme can influence the Call Admission Control (CAC) rules. On the contrary, for a BE service, users accept a variable bandwidth allocation, they are not subject to CAC and their pricing policies, according to the Proportional Fairness Pricing, are integrated within the flow control. In this paper we investigate the condition where both BE traffic and traffic explicitly requiring QoS (Guaranteed Performance, GP) are present. We propose three CAC rules for the GP traffic. The aim is to maximize the Internet Service Providers overall revenue and to establish a bound over the GP traffic prices. Numerical results are presented to show the good performance of the proposed techniques.

Approximating Optimal Estimation of Time Offset Synchronization With Temperature Variations

This paper addresses the problem of time offset synchronization in the presence of temperature variations, which lead to a non-Gaussian environment. In this context, regular Kalman filtering reveals to be suboptimal. A functional optimization approach is developed in order to approximate optimal estimation of the clock offset between master and slave. A numerical approximation is provided to this aim, based on regular neural network training. Other heuristics are provided as well, based on spline regression. An extensive performance evaluation highlights the benefits of the proposed techniques, which can be easily generalized to several clock synchronization protocols and operating environments.

On-line Bandwidth Control for Quality of Service Mapping over Satellite Independent Service Access Points

In the broadband satellite multimedia (BSM) architecture, developed by the European Telecommunications Standardizatlon Institute (ETSI), the physical layers are isolated from the rest by a satellite independent-service access point (SI-SAP). For technological reasons, satellite independent (SI) traffic accesses, requiring different QoS guarantees, must be aggregated together within the satellite dependent (SD) core and may change encapsulation format. Moreover, SD layers must assure proper fading countermeasures to face satellite channel radiation. In this work, we investigate a novel control algorithm to tackle the envisaged problems. Simulation results update the proposed approach

Detection of DoS attacks through Fourier transform and mutual information

Due to their recent appearance and the reduced requirements in terms of network bandwidth, Slow Denial of Service Attacks detection represents a particularly challenging problem. This paper presents a novel detection method, analyzing spectral features of the network traffic over small time horizons. The proposed method has been validated by extrapolating data referred to real traffic traces, elaborated over the Local Area Network of our research institute. We have considered different kinds of attacks and results show how the proposed approach is reliable and applicable also in other cybersecurity contexts.

Simple protocol enhancements of Rapid Spanning Tree Protocol over ring topologies

The paper addresses resilience over Ethernet networks using the Rapid Spanning Tree Protocol (RSTP). The topic constitutes an open issue of debate among the scientific and industrial community, as clear indications on the real RSTP performance for network recovery can hardly be found in the literature. Actually, the complicated protocol structure makes the analysis intricate and unsuitable for generalization. Moreover, the presence of other resilience algorithms, whose mechanisms and rules are explicitly designed for resilience, solves the problem beyond the application of RSTP. Even though those solutions are actually more efficient than RSTP, they are more expensive. In this perspective, the purposes of this paper are twofold. (1) First, it aims at critically evaluating the intrinsic limitations of RSTP. (2) Secondly, it proposes some simple protocol modifications to speed up reactions to network faults. Ring topologies are taken into account. As a result, the proposed modifications allow to assess how and when the protocol achieves almost-ideal performance. The performance analysis, made by simulations and via a testbed, validate the achievable performance as a trade-off between fast reactions and bandwidth overhead.

A Decision Theoretic Approach to Gaussian Sensor Networks

We consider the acquisition of measurements from a source, representing a physical phenomenon, by means of sensors deployed at different distances, and measuring random variables that are correlated with the source output. The acquired values are transmitted to a sink, where an estimation of the source has to be constructed, according to a given distortion criterion. In the presence of Gaussian random variables and a Gaussian vector channel, we are seeking optimum real-time joint source-channel encoder-decoder pairs that achieve a distortion sufficiently close to the theoretically optimal one, under a global power constraint, by activating only a subset of the sensors. The problem is posed in a team decision theoretic framework, and the optimal strategies are approximated by means of neural networks. We compare the solution with the results obtained by heuristically choosing a subset of the sensors on the basis of successive simulations under a fixed topology.

Optimal Bandwidth Provision at WiMAX MAC Service Access Point on Uplink Direction

In this paper, the IEEE 802.16 protocol is investigated with respect to the bandwidth provision problem arising at the medium access control (MAC) layer. The aim is to optimally tune the resource allocation to match QoS requirements. Traffic flows are originated at network layers overlying the 802.16 protocol stack. This leads to the investigation of a novel control algorithm, suited to optimal bandwidth allocation and call admission control in the presence of statistically heterogeneous flows. Specific implementation details are provided to match the application of the control algorithm using the regular 802.16 request-grant protocol. Simulation results validate the proposed approach.