Piet Van Mieghem - Academia.edu (original) (raw)
Papers by Piet Van Mieghem
Lecture Notes in Computer Science, 2010
More and more free multi-party video conferencing applications are readily available over the Int... more More and more free multi-party video conferencing applications are readily available over the Internet and both Server-to-Client (S/C) or Peer-to-Peer (P2P) technologies are used. Investigating their mechanisms, analyzing their system performance, and measuring their quality are important objectives for researchers, developers and end users. In this paper, we take four representative video conferencing applications and reveal their characteristics and different aspects of Quality of Experience. Based on our observations and analysis, we recommend to incorporate the following aspects when designing video conferencing applications: 1) Traffic load control/balancing algorithms to better use the limited bandwidth resources and to have a stable conversation; 2) Use traffic shaping policy or adaptively re-encode streams in real time to limit the overall traffic. This work is, to our knowledge, the first measurement work to study and compare mechanisms and performance of existing free multi-party video conferencing systems.
Random Structures and Algorithms, 2004
Quality of Future Internet Services, 2004
Journal of Accounting Research, 2007
ABSTRACT In this paper we study the spectral radius of a number of real-life networks. This study... more ABSTRACT In this paper we study the spectral radius of a number of real-life networks. This study is motivated by the fact that the smaller the spectral radius, the higher the robustness of a network against the spread of viruses. First we study how well-known upper bounds for the spectral radius of graphs match to the spectral radii of the social network of the Dutch soccer team, the Dutch roadmap network, the network of the observable part of the Internet graph at the IP-level and the autonomous system level. Secondly, we compare the spectral radius for these real-life networks with those of commonly used complex network models
Proceedings of the First International ICST Conference on Simulation Tools and Techniques for Communications Networks and Systems, 2008
In this paper we present DeSiNe, a modular flow-level network simulator. DeSiNe is aimed at perfo... more In this paper we present DeSiNe, a modular flow-level network simulator. DeSiNe is aimed at performance analysis and benchmarking of Quality of Service routing algorithms and traffic engineering extensions. Several well-known QoS routing algorithms and traffic engineering extensions have been implemented in De-SiNe. The flow-level nature provides scalability, such that large networks and heavy-traffic conditions are possible. In this paper, the functional and structural design of DeSiNe are presented and the usability and various features are illustrated by means of several examples. The source code of DeSiNe is publicly available.
2006 Symposium on Communications and Vehicular Technology, 2006
In this paper we study the spectral radius of a number of real-life networks. This study is motiv... more In this paper we study the spectral radius of a number of real-life networks. This study is motivated by the fact that the smaller the spectral radius, the higher the robustness of a network against the spread of viruses. First we study how wellknown upper bounds for the spectral radius of graphs match to the spectral radii of the social network of the Dutch soccer team, the Dutch roadmap network, the network of the observable part of the Internet graph at the IP-level and the Autonomous System level. Secondly, we compare the spectral radius for these real-life networks with those of commonly used complex network models.
Chaos: An Interdisciplinary Journal of Nonlinear Science, 2015
The identification of clusters or communities in complex networks is a reappearing problem. The m... more The identification of clusters or communities in complex networks is a reappearing problem. The minimum spanning tree (MST), the tree connecting all nodes with minimum total weight, is regarded as an important transport backbone of the original weighted graph. We hypothesize that the clustering of the MST reveals insight in the hierarchical structure of weighted graphs. However, existing theories and algorithms have difficulties to define and identify clusters in trees. Here, we first define clustering in trees and then propose a tree agglomerative hierarchical clustering (TAHC) method for the detection of clusters in MSTs. We then demonstrate that the TAHC method can detect clusters in artificial trees, and also in MSTs of weighted social networks, for which the clusters are in agreement with the previously reported clusters of the original weighted networks. Our results therefore not only indicate that clusters can be found in MSTs, but also that the MSTs contain information about the underlying clusters of the original weighted network.
2008 The Second International Conference on Next Generation Mobile Applications, Services, and Technologies, 2008
Peer-to-Peer (P2P) file sharing has become immensely popular in the Internet. Recently, there has... more Peer-to-Peer (P2P) file sharing has become immensely popular in the Internet. Recently, there has been a growing interest in academic and commercial enviornments for live streaming using P2P technology. A number of new P2P digital television (P2PTV) applications have emerged. Such P2PTV applications are developed with proprietary technologies and the Quality of Experience (QoE) provided by them is not well known. Therefore, investigating their mechanisms, analyzing their performance, and measuring their quality are important for researchers, operators and end users. In this paper, we present results from a measurement study of a P2PTV application called SopCast, using both objective and subjective measurement technologies. The results obtained in our study reveal important design issues of SopCast and the QoE that the end users perceive.
Proceedings.Twenty-First Annual Joint Conference of the IEEE Computer and Communications Societies, 2002
Most of the currently deployed multicast protocols (e.g. DVMRP, PIM, MOSPF) build one shortest pa... more Most of the currently deployed multicast protocols (e.g. DVMRP, PIM, MOSPF) build one shortest path multicast tree per sender, the tree being rooted at the sender's subnetwork. This paper examines the stability of such a tree, specifically, "How does the number of links change as the number of multicast users in a group changes?" Two modelling assumptions are made. We assume that (a) packets are delivered along the shortest path tree (which is a realistic assumption as indicated above) and that (b) the m multicast group member nodes are chosen uniformly out of the total number of nodes N. The probability density function for the number of changed edges ∆N (m) when one multicast user joins or leaves the group is studied. For random graphs of the class Gp (N) with N nodes, link density p and with uniformly (or exponentially) distributed link weights, the probability density function Pr [∆N (m) = k] is proved to tend to a Poisson distribution for large N. The proof of this theorem enables a generalization to an arbitrary topology. Simulations, mainly conducted to quantify the validity of the asymptotic regime, reveal that the Poisson law seems more widely valid than just in the asymptotic regime where N → ∞. In addition, the effect of the link weight distribution on the stability of the multicast tree is investigated. Finally, the stability of a Steiner tree connecting m multicast users is compared to the shortest path tree via simulations.
2008 Tenth IEEE International Symposium on Multimedia, 2008
Recently, there has been a growing interest in academic and commercial environments for Video-on-... more Recently, there has been a growing interest in academic and commercial environments for Video-on-Demand (VoD) using technology. Unlike centralized solutions for VoD services, P2P technology lets the clients distribute video content among themselves. In this paper, we propose an analytical model for P2PVoD and we compare that model to a realistic P2PVoD simulator. With our model, parameters that affect the system performance can be observed, and the system stability can be investigated. Our model leads to design rules for achieving a good and stable system performance. This work is, to our knowledge, the first analytical work to model mesh-based P2PVoD.
The problem of finding multi-constrained paths has been addressed by several QoS routing algorith... more The problem of finding multi-constrained paths has been addressed by several QoS routing algorithms. While they generally satisfy the application requirements, they often do not consider the perspective of service providers. Service providers aim at maximizing the throughput and the number of accepted requests. These goals have been addressed by traffic engineering algorithms considering bandwidth as the sole application requirement. We propose a proper length function for an existing QoS routing algorithm (SAMCRA) that attempts to optimize network utilization while still offering QoS guarantees. This paper presents a comparison between several proposed algorithms via simulation studies. The simulations show that SAMCRA with a proper length performs similarly or even better than the best among the other algorithms and it has a fast running time.
Lecture Notes in Computer Science, 2009
In recent years, a number of commercial peer-to-peer TV (P2PTV) applications have been launched. ... more In recent years, a number of commercial peer-to-peer TV (P2PTV) applications have been launched. Yet, their mechanisms and characteristics are unknown. In this paper, we study SopCast, a typical proprietary P2PTV system. Treating SopCast as a black box, we perform a set of experiments that are suitable to analyze SopCast in depth. We attempt to disclose the SopCast protocol. The
Physical Review E, 2014
We consider a model for the diffusion of epidemics in a population that is partitioned into local... more We consider a model for the diffusion of epidemics in a population that is partitioned into local communities. In particular, assuming a mean-field approximation, we analyze a continuous-time susceptible-infected-susceptible (SIS) model that has appeared recently in the literature. The probability by which an individual infects individuals in its own community is different from the probability of infecting individuals in other communities. The aim of the model, compared to the standard, nonclustered one, is to provide a compact description for the presence of communities of local infection where the epidemic process is faster compared to the rate at which it spreads across communities. Ultimately, it provides a tool to express the probability of epidemic outbreaks in the form of a metastable infection probability. In the proposed model, the spatial structure of the network is encoded by the adjacency matrix of clusters, i.e., the connections between local communities, and by the vector of the sizes of local communities. Thus, the existence of a nontrivial metastable occupancy probability is determined by an epidemic threshold which depends on the clusters' size and on the intercommunity network structure.
Lecture Notes in Computer Science, 2003
Constraint-based routing is an invaluable part of a full-fledged Quality of Service architecture.... more Constraint-based routing is an invaluable part of a full-fledged Quality of Service architecture. Unfortunately, QoS routing with multiple additive constraints is known to be a NP-complete problem. Hence, accurate constraint-based routing algorithms with a fast running time are scarce, perhaps even non-existent. The need for such algorithms has resulted in the proposal of numerous heuristics and a few exact solutions. This chapter presents a thorough, concise, and fair evaluation of the most important multi-constrained path selection algorithms known today. A performance evaluation of these algorithms is presented based on a complexity analysis and simulation results. Besides the routing algorithm, dynamic aspects of QoS routing are discussed: how to cope with incomplete or inaccurate topology information and (in)stability issues.
Random Structures and Algorithms, 2002
In this paper we study the covariance structure of the number of nodes k and l steps away from th... more In this paper we study the covariance structure of the number of nodes k and l steps away from the root in random recursive trees. We give an analytic expression valid for all k, l and tree sizes N . The fraction of nodes k steps away from the root is a random probability distribution in k. The expression for the covariances allows us to show that the total variation distance between this (random) probability distribution and its mean converges in probability to zero.
Random Structures and Algorithms, 2007
The minimal weight of the shortest path tree in a complete graph with independent and exponential... more The minimal weight of the shortest path tree in a complete graph with independent and exponential (mean 1) random link weights, is shown to converge to a Gaussian distribution. We prove a conditional central limit theorem and show that the condition holds with probability converging to 1.
Random Structures and Algorithms, 2005
In this paper we study a random graph with N nodes, where node j has degree D j and
Probability in the Engineering and Informational Sciences, 2001
We study first passage percolation on the random graph G p (N ) with exponentially distributed we... more We study first passage percolation on the random graph G p (N ) with exponentially distributed weights on the links. For the special case of the complete graph, we show that this problem can be described in terms of a continuous time Markov chain and recursive trees. The Markov chain X(t) describes the number of nodes that can be reached from the initial node in time t. The recursive trees, which are uniform trees of N nodes, describe the structure of the cluster once it contains all the nodes of the complete graph. We compute the distribution of the number hops of the shortest path between two arbitrary nodes.
Physical Review E, 2010
Brain functioning such as cognitive performance depends on the functional interactions between br... more Brain functioning such as cognitive performance depends on the functional interactions between brain areas, namely, the functional brain networks. The functional brain networks of a group of patients with brain tumors are measured before and after tumor resection. In this work, we perform a weighted network analysis to understand the effect of neurosurgery on the characteristics of functional brain networks. Statistically significant changes in network features have been discovered in the beta ͑13-30 Hz͒ band after neurosurgery: the link weight correlation around nodes and within triangles increases which implies improvement in local efficiency of information transfer and robustness; the clustering of high link weights in a subgraph becomes stronger, which enhances the global transport capability; and the decrease in the synchronization or virus spreading threshold, revealed by the increase in the largest eigenvalue of the adjacency matrix, which suggests again the improvement of information dissemination.
Physical Review E, 2014
When two viruses compete for healthy nodes in a simple network and both spreading rates are above... more When two viruses compete for healthy nodes in a simple network and both spreading rates are above the epidemic threshold, only one virus will survive. However, if we prevent the viruses from dying out, rich dynamics emerge. When both viruses are identical, one virus always dominates the other, but the dominating and dominated virus alternate. We show in the complete graph that the domination time depends on the total number of infected nodes at the beginning of the domination period and, moreover, that the distribution of the domination time decays exponentially yet slowly. When the viruses differ moderately in strength and/or speed the weaker and/or slower virus can still dominate the other but for a short time. Interestingly, depending on the number of infected nodes at the start of a domination period, being quicker can be a disadvantage.
Lecture Notes in Computer Science, 2010
More and more free multi-party video conferencing applications are readily available over the Int... more More and more free multi-party video conferencing applications are readily available over the Internet and both Server-to-Client (S/C) or Peer-to-Peer (P2P) technologies are used. Investigating their mechanisms, analyzing their system performance, and measuring their quality are important objectives for researchers, developers and end users. In this paper, we take four representative video conferencing applications and reveal their characteristics and different aspects of Quality of Experience. Based on our observations and analysis, we recommend to incorporate the following aspects when designing video conferencing applications: 1) Traffic load control/balancing algorithms to better use the limited bandwidth resources and to have a stable conversation; 2) Use traffic shaping policy or adaptively re-encode streams in real time to limit the overall traffic. This work is, to our knowledge, the first measurement work to study and compare mechanisms and performance of existing free multi-party video conferencing systems.
Random Structures and Algorithms, 2004
Quality of Future Internet Services, 2004
Journal of Accounting Research, 2007
ABSTRACT In this paper we study the spectral radius of a number of real-life networks. This study... more ABSTRACT In this paper we study the spectral radius of a number of real-life networks. This study is motivated by the fact that the smaller the spectral radius, the higher the robustness of a network against the spread of viruses. First we study how well-known upper bounds for the spectral radius of graphs match to the spectral radii of the social network of the Dutch soccer team, the Dutch roadmap network, the network of the observable part of the Internet graph at the IP-level and the autonomous system level. Secondly, we compare the spectral radius for these real-life networks with those of commonly used complex network models
Proceedings of the First International ICST Conference on Simulation Tools and Techniques for Communications Networks and Systems, 2008
In this paper we present DeSiNe, a modular flow-level network simulator. DeSiNe is aimed at perfo... more In this paper we present DeSiNe, a modular flow-level network simulator. DeSiNe is aimed at performance analysis and benchmarking of Quality of Service routing algorithms and traffic engineering extensions. Several well-known QoS routing algorithms and traffic engineering extensions have been implemented in De-SiNe. The flow-level nature provides scalability, such that large networks and heavy-traffic conditions are possible. In this paper, the functional and structural design of DeSiNe are presented and the usability and various features are illustrated by means of several examples. The source code of DeSiNe is publicly available.
2006 Symposium on Communications and Vehicular Technology, 2006
In this paper we study the spectral radius of a number of real-life networks. This study is motiv... more In this paper we study the spectral radius of a number of real-life networks. This study is motivated by the fact that the smaller the spectral radius, the higher the robustness of a network against the spread of viruses. First we study how wellknown upper bounds for the spectral radius of graphs match to the spectral radii of the social network of the Dutch soccer team, the Dutch roadmap network, the network of the observable part of the Internet graph at the IP-level and the Autonomous System level. Secondly, we compare the spectral radius for these real-life networks with those of commonly used complex network models.
Chaos: An Interdisciplinary Journal of Nonlinear Science, 2015
The identification of clusters or communities in complex networks is a reappearing problem. The m... more The identification of clusters or communities in complex networks is a reappearing problem. The minimum spanning tree (MST), the tree connecting all nodes with minimum total weight, is regarded as an important transport backbone of the original weighted graph. We hypothesize that the clustering of the MST reveals insight in the hierarchical structure of weighted graphs. However, existing theories and algorithms have difficulties to define and identify clusters in trees. Here, we first define clustering in trees and then propose a tree agglomerative hierarchical clustering (TAHC) method for the detection of clusters in MSTs. We then demonstrate that the TAHC method can detect clusters in artificial trees, and also in MSTs of weighted social networks, for which the clusters are in agreement with the previously reported clusters of the original weighted networks. Our results therefore not only indicate that clusters can be found in MSTs, but also that the MSTs contain information about the underlying clusters of the original weighted network.
2008 The Second International Conference on Next Generation Mobile Applications, Services, and Technologies, 2008
Peer-to-Peer (P2P) file sharing has become immensely popular in the Internet. Recently, there has... more Peer-to-Peer (P2P) file sharing has become immensely popular in the Internet. Recently, there has been a growing interest in academic and commercial enviornments for live streaming using P2P technology. A number of new P2P digital television (P2PTV) applications have emerged. Such P2PTV applications are developed with proprietary technologies and the Quality of Experience (QoE) provided by them is not well known. Therefore, investigating their mechanisms, analyzing their performance, and measuring their quality are important for researchers, operators and end users. In this paper, we present results from a measurement study of a P2PTV application called SopCast, using both objective and subjective measurement technologies. The results obtained in our study reveal important design issues of SopCast and the QoE that the end users perceive.
Proceedings.Twenty-First Annual Joint Conference of the IEEE Computer and Communications Societies, 2002
Most of the currently deployed multicast protocols (e.g. DVMRP, PIM, MOSPF) build one shortest pa... more Most of the currently deployed multicast protocols (e.g. DVMRP, PIM, MOSPF) build one shortest path multicast tree per sender, the tree being rooted at the sender's subnetwork. This paper examines the stability of such a tree, specifically, "How does the number of links change as the number of multicast users in a group changes?" Two modelling assumptions are made. We assume that (a) packets are delivered along the shortest path tree (which is a realistic assumption as indicated above) and that (b) the m multicast group member nodes are chosen uniformly out of the total number of nodes N. The probability density function for the number of changed edges ∆N (m) when one multicast user joins or leaves the group is studied. For random graphs of the class Gp (N) with N nodes, link density p and with uniformly (or exponentially) distributed link weights, the probability density function Pr [∆N (m) = k] is proved to tend to a Poisson distribution for large N. The proof of this theorem enables a generalization to an arbitrary topology. Simulations, mainly conducted to quantify the validity of the asymptotic regime, reveal that the Poisson law seems more widely valid than just in the asymptotic regime where N → ∞. In addition, the effect of the link weight distribution on the stability of the multicast tree is investigated. Finally, the stability of a Steiner tree connecting m multicast users is compared to the shortest path tree via simulations.
2008 Tenth IEEE International Symposium on Multimedia, 2008
Recently, there has been a growing interest in academic and commercial environments for Video-on-... more Recently, there has been a growing interest in academic and commercial environments for Video-on-Demand (VoD) using technology. Unlike centralized solutions for VoD services, P2P technology lets the clients distribute video content among themselves. In this paper, we propose an analytical model for P2PVoD and we compare that model to a realistic P2PVoD simulator. With our model, parameters that affect the system performance can be observed, and the system stability can be investigated. Our model leads to design rules for achieving a good and stable system performance. This work is, to our knowledge, the first analytical work to model mesh-based P2PVoD.
The problem of finding multi-constrained paths has been addressed by several QoS routing algorith... more The problem of finding multi-constrained paths has been addressed by several QoS routing algorithms. While they generally satisfy the application requirements, they often do not consider the perspective of service providers. Service providers aim at maximizing the throughput and the number of accepted requests. These goals have been addressed by traffic engineering algorithms considering bandwidth as the sole application requirement. We propose a proper length function for an existing QoS routing algorithm (SAMCRA) that attempts to optimize network utilization while still offering QoS guarantees. This paper presents a comparison between several proposed algorithms via simulation studies. The simulations show that SAMCRA with a proper length performs similarly or even better than the best among the other algorithms and it has a fast running time.
Lecture Notes in Computer Science, 2009
In recent years, a number of commercial peer-to-peer TV (P2PTV) applications have been launched. ... more In recent years, a number of commercial peer-to-peer TV (P2PTV) applications have been launched. Yet, their mechanisms and characteristics are unknown. In this paper, we study SopCast, a typical proprietary P2PTV system. Treating SopCast as a black box, we perform a set of experiments that are suitable to analyze SopCast in depth. We attempt to disclose the SopCast protocol. The
Physical Review E, 2014
We consider a model for the diffusion of epidemics in a population that is partitioned into local... more We consider a model for the diffusion of epidemics in a population that is partitioned into local communities. In particular, assuming a mean-field approximation, we analyze a continuous-time susceptible-infected-susceptible (SIS) model that has appeared recently in the literature. The probability by which an individual infects individuals in its own community is different from the probability of infecting individuals in other communities. The aim of the model, compared to the standard, nonclustered one, is to provide a compact description for the presence of communities of local infection where the epidemic process is faster compared to the rate at which it spreads across communities. Ultimately, it provides a tool to express the probability of epidemic outbreaks in the form of a metastable infection probability. In the proposed model, the spatial structure of the network is encoded by the adjacency matrix of clusters, i.e., the connections between local communities, and by the vector of the sizes of local communities. Thus, the existence of a nontrivial metastable occupancy probability is determined by an epidemic threshold which depends on the clusters' size and on the intercommunity network structure.
Lecture Notes in Computer Science, 2003
Constraint-based routing is an invaluable part of a full-fledged Quality of Service architecture.... more Constraint-based routing is an invaluable part of a full-fledged Quality of Service architecture. Unfortunately, QoS routing with multiple additive constraints is known to be a NP-complete problem. Hence, accurate constraint-based routing algorithms with a fast running time are scarce, perhaps even non-existent. The need for such algorithms has resulted in the proposal of numerous heuristics and a few exact solutions. This chapter presents a thorough, concise, and fair evaluation of the most important multi-constrained path selection algorithms known today. A performance evaluation of these algorithms is presented based on a complexity analysis and simulation results. Besides the routing algorithm, dynamic aspects of QoS routing are discussed: how to cope with incomplete or inaccurate topology information and (in)stability issues.
Random Structures and Algorithms, 2002
In this paper we study the covariance structure of the number of nodes k and l steps away from th... more In this paper we study the covariance structure of the number of nodes k and l steps away from the root in random recursive trees. We give an analytic expression valid for all k, l and tree sizes N . The fraction of nodes k steps away from the root is a random probability distribution in k. The expression for the covariances allows us to show that the total variation distance between this (random) probability distribution and its mean converges in probability to zero.
Random Structures and Algorithms, 2007
The minimal weight of the shortest path tree in a complete graph with independent and exponential... more The minimal weight of the shortest path tree in a complete graph with independent and exponential (mean 1) random link weights, is shown to converge to a Gaussian distribution. We prove a conditional central limit theorem and show that the condition holds with probability converging to 1.
Random Structures and Algorithms, 2005
In this paper we study a random graph with N nodes, where node j has degree D j and
Probability in the Engineering and Informational Sciences, 2001
We study first passage percolation on the random graph G p (N ) with exponentially distributed we... more We study first passage percolation on the random graph G p (N ) with exponentially distributed weights on the links. For the special case of the complete graph, we show that this problem can be described in terms of a continuous time Markov chain and recursive trees. The Markov chain X(t) describes the number of nodes that can be reached from the initial node in time t. The recursive trees, which are uniform trees of N nodes, describe the structure of the cluster once it contains all the nodes of the complete graph. We compute the distribution of the number hops of the shortest path between two arbitrary nodes.
Physical Review E, 2010
Brain functioning such as cognitive performance depends on the functional interactions between br... more Brain functioning such as cognitive performance depends on the functional interactions between brain areas, namely, the functional brain networks. The functional brain networks of a group of patients with brain tumors are measured before and after tumor resection. In this work, we perform a weighted network analysis to understand the effect of neurosurgery on the characteristics of functional brain networks. Statistically significant changes in network features have been discovered in the beta ͑13-30 Hz͒ band after neurosurgery: the link weight correlation around nodes and within triangles increases which implies improvement in local efficiency of information transfer and robustness; the clustering of high link weights in a subgraph becomes stronger, which enhances the global transport capability; and the decrease in the synchronization or virus spreading threshold, revealed by the increase in the largest eigenvalue of the adjacency matrix, which suggests again the improvement of information dissemination.
Physical Review E, 2014
When two viruses compete for healthy nodes in a simple network and both spreading rates are above... more When two viruses compete for healthy nodes in a simple network and both spreading rates are above the epidemic threshold, only one virus will survive. However, if we prevent the viruses from dying out, rich dynamics emerge. When both viruses are identical, one virus always dominates the other, but the dominating and dominated virus alternate. We show in the complete graph that the domination time depends on the total number of infected nodes at the beginning of the domination period and, moreover, that the distribution of the domination time decays exponentially yet slowly. When the viruses differ moderately in strength and/or speed the weaker and/or slower virus can still dominate the other but for a short time. Interestingly, depending on the number of infected nodes at the start of a domination period, being quicker can be a disadvantage.