Particle swarm optimization for the Steiner tree in graph and delay-constrained multicast routing problems

This paper presents the first investigation on applying a particle swarm optimization (PSO) algorithm to both the Steiner tree problem and the delay constrained multicast routing problem. Steiner tree problems, being the underlining models of many applications, have received significant research attention within the meta-heuristics community. The literature on the application of meta-heuristics to multicast routing problems is less extensive but includes several promising approaches. Many interesting research issues still remain to be investigated, for example, the inclusion of different constraints, such as delay bounds, when finding multicast trees with minimum cost. In this paper, we develop a novel PSO algorithm based on the jumping PSO (JPSO) algorithm recently developed by Moreno-Perez et al. (Proc. of the 7th Metaheuristics International Conference, 2007), and also propose two novel local search heuristics within our JPSO framework. A path replacement operator has been used in particle moves to improve the positions of the particle with regard to the structure of the tree. We test the performance of our JPSO algorithm, and the effect of the integrated local search heuristics by an extensive set of experiments on multicast routing benchmark problems and Steiner tree problems from the OR library. The experimental results show the superior performance of the proposed JPSO algorithm over a number of other state-of-the-art approaches

The Steiner Tree Problem with Delays: A compact formulation and reduction procedures

This paper investigates the Steiner Tree Problem with Delays (STPD), a variation of the classical Steiner Tree problem that arises in multicast routing. We propose an exact solution approach that is based on a polynomial-size formulation for this challenging NP-hard problem. The LP relaxation of this formulation is enhanced through the derivation of new lifted Miller-Tucker-Zemlin subtour elimination constraints. Furthermore, we present several preprocessing techniques for both reducing the problem size and tightening the LP relaxation. Finally, we report the results of extensive computational experiments on instances with up to 1000 nodes. These results attest to the efficacy of the combination of the enhanced formulation and reduction techniques

A constrained steiner tree approach for reconstructions of multicast trees.

Sun Tong.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.Includes bibliographical references (leaves 77-81).Abstracts in English and Chinese.Chinese Abstract --- p.IAbstract --- p.IIAcknowledgements --- p.IIIList of Contents --- p.IVList of Figures --- p.VIIChapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Multicast Routing Problem --- p.1Chapter 1.2 --- Constrained multicast routing problem and SSRA algorithm --- p.4Chapter 1.3 --- Thesis organization --- p.7Chapter Chapter 2 --- Constrained Multicast Routing Algorithms --- p.8Chapter 2.1 --- Steiner tree heuristic --- p.8Chapter 2.1.1 --- Shortest Paths Heuristic --- p.9Chapter 2.1.2 --- Distance Network Heuristic --- p.10Chapter 2.2 --- Review of existing constrained multicast routing algorithms --- p.10Chapter 2.2.1 --- Static group member --- p.10Chapter 2.2.2 --- Dynamic group member --- p.14Chapter 2.2.2.1 --- Non-rearrangeable --- p.15Chapter 2.2.2.2 --- Rearrangeable --- p.23Chapter Chapter 3 --- Small Scale Rearrangement Algorithm for Multicast Routing --- p.32Chapter 3.1 --- Problem formulation --- p.32Chapter 3.1.1 --- Network Model --- p.32Chapter 3.1.2 --- Problem Specification --- p.33Chapter 3.1.3 --- Definitions and Notations --- p.36Chapter 3.2 --- Local Checking Scheme (LCS) --- p.37Chapter 3.3 --- Small Scale Rearrangement Algorithm (SSRA) for Multicast Routing --- p.41Chapter 3.3.1 --- Static group membership --- p.42Chapter 3.3.2 --- Dynamic group membership --- p.43Chapter 3.3.2.1 --- Node addition --- p.44Chapter 3.3.2.2 --- Node removal --- p.44Chapter 3.3.2.3 --- General steps --- p.45Chapter 3.3.2.4 --- Example --- p.47Chapter Chapter 4 --- Analysis --- p.50Chapter Chapter 5 --- Simulations --- p.54Chapter 5.1 --- Simulation Model --- p.54Chapter 5.2 --- Simulation Parameters Parameter Default Value/Generating Method --- p.56Chapter 5.3 --- Performance Metrics --- p.58Chapter 5.4 --- Discussion of Results --- p.59Chapter 5.4.1 --- Group 1: static group membership --- p.59Chapter 5.4.2 --- Group 2: dynamic group membership --- p.63Chapter 5.4.3 --- Comparison --- p.69Chapter 5.5 --- Implementation Issue --- p.73Chapter Chapter 6 --- Conclusion --- p.75Reference --- p.7

A Source-Based Algorithm For Delay-Constrained Minimum-Cost Multicasting

A new heuristic algorithm is presented for constructing minimum-cost multicast trees with delay constraints. The new algorithm can set variable delay bounds on destinations and handles two variants of the network cost optimization goal: one minimizing the total cost (total bandwidth utilization) of the tree, and another minimizing the maximal link cost (the most congested link). Instead of the single-pass tree construction approach used in most previous heuristics, the new algorithm is based on a feasible search optimization method which starts with the minimumdelay tree and monotonically decreases the cost by iterative improvement of the delay-bounded tree. The optimality of the costs of the delay-bounded trees obtained with the new algorithm is analyzed by simulation. Depending on how tight the delay bounds are, the costs of the multicast trees obtained with the new algorithm are shown to be very close to the costs of the trees obtained by the Kou, Markowsky and Berman's algorithm. ..

Quality of service routing on wide area networks.

Moore [20] introduced the quickest path problem and it has been studied extensively in recent times. The quickest path problem is to determine a routing path to minimize end-to-end delay from the source to the destination node taking into account message size, and propagation delay and bandwidth on the links of the network. Thus the quickest path is a path with minimum end-to-end delay time required to send sigma units of message from a source node to the destination node.The main theme of this dissertation is to investigate unicast and multicast routing algorithms in wide area networks. Towards this end, first we present a unifying quickest path algorithm for different message transfer modes at intermediate nodes. The source to destination path varies with message sizes. Quickest path algorithms build a table called the Path-Table that when searched with message size gives the minimum end-to-end delay path for that message size. Our second result deals with efficient construction of the Path-Table when a link or path bandwidth changes, where path bandwidth is defined as the minimum of the bandwidths on the links of the path. Third, we present efficient algorithms for all-to-all quickest path problems in the presence of unreliable links in the network. By assigning probability of link failure to each link we can cast two problems namely, quickest most reliable path and most reliable quickest path.Routing is the process of sending a message from a source node to the destination node and the routing algorithm is a method to determine links that a message should be transmitted in order to reach the destination. The routing algorithm can be classified into the following three categories: unicast, multicast, and broadcast. Unicast involves sending a message from a given source to a destination; multicasting is a mechanism to send a message from a given source to a chosen set of destinations; broadcasting is sending a message from a given source to all the nodes in the network. Clearly, unicast and broadcast are special cases of multicast. The path selected by a routing algorithm depends on the application's Quality-of-Service (QoS) demands such as, end-to-end delay time, cost, delay jitter, and other factors.Our fourth result deals with multicast routing in wide area networks. We have developed several heuristics for the construction of a multicast tree that minimizes end-to-end delay time taking into account message size, and propagation delay and bandwidths on links. We consider different modes of message transfers at intermediate nodes and for each type of intermediate node architecture we present heuristics for the multicast tree construction. The heuristics are simulated on large networks that are generated using different network generation models including Waxman I and II, Locality, and Transit-Stub. Our heuristics are shown to outperform existing heuristics that are based on shortest path and minimum spanning tree for multicast tree construction. Finally, we introduce a novel heuristic for the construction of a multicast tree with minimum cost in Internet like topologies. Our algorithm on directed asymmetric networks is shown to have a performance gain in terms of tree costs over existing algorithms

Quality of service aware data dissemination in vehicular Ad Hoc networks

Des systèmes de transport intelligents (STI) seront éventuellement fournis dans un proche avenir pour la sécurité et le confort des personnes lors de leurs déplacements sur les routes. Les réseaux ad-hoc véhiculaires (VANETs) représentent l'élément clé des STI. Les VANETs sont formés par des véhicules qui communiquent entre eux et avec l'infrastructure. En effet, les véhicules pourront échanger des messages qui comprennent, par exemple, des informations sur la circulation routière, les situations d'urgence et les divertissements. En particulier, les messages d'urgence sont diffusés par des véhicules en cas d'urgence (p.ex. un accident de voiture); afin de permettre aux conducteurs de réagir à temps (p.ex., ralentir), les messages d'urgence doivent être diffusés de manière fiable dans un délai très court. Dans les VANETs, il existe plusieurs facteurs, tels que le canal à pertes, les terminaux cachés, les interférences et la bande passante limitée, qui compliquent énormément la satisfaction des exigences de fiabilité et de délai des messages d'urgence. Dans cette thèse, en guise de première contribution, nous proposons un schéma de diffusion efficace à plusieurs sauts, appelé Dynamic Partitioning Scheme (DPS), pour diffuser les messages d'urgence. DPS calcule les tailles de partitions dynamiques et le calendrier de transmission pour chaque partition; à l'intérieur de la zone arrière de l'expéditeur, les partitions sont calculées de sorte qu'en moyenne chaque partition contient au moins un seul véhicule; l'objectif est de s'assurer que seul un véhicule dans la partition la plus éloignée (de l'expéditeur) est utilisé pour diffuser le message, jusqu'au saut suivant; ceci donne lieu à un délai d'un saut plus court. DPS assure une diffusion rapide des messages d'urgence. En outre, un nouveau mécanisme d'établissement de liaison, qui utilise des tonalités occupées, est proposé pour résoudre le problème du problème de terminal caché. Dans les VANETs, la Multidiffusion, c'est-à-dire la transmission d'un message d'une source à un nombre limité de véhicules connus en tant que destinations, est très importante. Par rapport à la diffusion unique, avec Multidiffusion, la source peut simultanément prendre en charge plusieurs destinations, via une arborescence de multidiffusion, ce qui permet d'économiser de la bande passante et de réduire la congestion du réseau. Cependant, puisque les VANETs ont une topologie dynamique, le maintien de la connectivité de l'arbre de multidiffusion est un problème majeur. Comme deuxième contribution, nous proposons deux approches pour modéliser l'utilisation totale de bande passante d'une arborescence de multidiffusion: (i) la première approche considère le nombre de segments de route impliqués dans l'arbre de multidiffusion et (ii) la seconde approche considère le nombre d'intersections relais dans l'arbre de multidiffusion. Une heuristique est proposée pour chaque approche. Pour assurer la qualité de service de l'arbre de multidiffusion, des procédures efficaces sont proposées pour le suivi des destinations et la surveillance de la qualité de service des segments de route. Comme troisième contribution, nous étudions le problème de la congestion causée par le routage du trafic de données dans les VANETs. Nous proposons (1) une approche de routage basée sur l’infonuagique qui, contrairement aux approches existantes, prend en compte les chemins de routage existants qui relaient déjà les données dans les VANETs. Les nouvelles demandes de routage sont traitées de sorte qu'aucun segment de route ne soit surchargé par plusieurs chemins de routage croisés. Au lieu d'acheminer les données en utilisant des chemins de routage sur un nombre limité de segments de route, notre approche équilibre la charge des données en utilisant des chemins de routage sur l'ensemble des tronçons routiers urbains, dans le but d'empêcher, dans la mesure du possible, les congestions locales dans les VANETs; et (2) une approche basée sur le réseau défini par logiciel (SDN) pour surveiller la connectivité VANET en temps réel et les délais de transmission sur chaque segment de route. Les données de surveillance sont utilisées en entrée de l'approche de routage.Intelligent Transportation Systems (ITS) will be eventually provided in the near future for both safety and comfort of people during their travel on the roads. Vehicular ad-hoc Networks (VANETs), represent the key component of ITS. VANETs consist of vehicles that communicate with each other and with the infrastructure. Indeed, vehicles will be able to exchange messages that include, for example, information about road traffic, emergency situations, and entertainment. Particularly, emergency messages are broadcasted by vehicles in case of an emergency (e.g., car accident); in order to allow drivers to react in time (e.g., slow down), emergency messages must be reliably disseminated with very short delay. In VANETs, there are several factors, such as lossy channel, hidden terminals, interferences and scarce bandwidth, which make satisfying reliability and delay requirements of emergency messages very challenging. In this thesis, as the first contribution, we propose a reliable time-efficient and multi-hop broadcasting scheme, called Dynamic Partitioning Scheme (DPS), to disseminate emergency messages. DPS computes dynamic partition sizes and the transmission schedule for each partition; inside the back area of the sender, the partitions are computed such that in average each partition contains at least a single vehicle; the objective is to ensure that only a vehicle in the farthest partition (from the sender) is used to disseminate the message, to next hop, resulting in shorter one hop delay. DPS ensures fast dissemination of emergency messages. Moreover, a new handshaking mechanism, that uses busy tones, is proposed to solve the problem of hidden terminal problem. In VANETs, Multicasting, i.e. delivering a message from a source to a limited known number of vehicles as destinations, is very important. Compared to Unicasting, with Multicasting, the source can simultaneously support multiple destinations, via a multicast tree, saving bandwidth and reducing overall communication congestion. However, since VANETs have a dynamic topology, maintaining the connectivity of the multicast tree is a major issue. As the second contribution, we propose two approaches to model total bandwidth usage of a multicast tree: (i) the first approach considers the number of road segments involved in the multicast tree and (ii) the second approach considers the number of relaying intersections involved in the multicast tree. A heuristic is proposed for each approach. To ensure QoS of the multicasting tree, efficient procedures are proposed for tracking destinations and monitoring QoS of road segments. As the third contribution, we study the problem of network congestion in routing data traffic in VANETs. We propose (1) a Cloud-based routing approach that, in opposition to existing approaches, takes into account existing routing paths which are already relaying data in VANETs. New routing requests are processed such that no road segment gets overloaded by multiple crossing routing paths. Instead of routing over a limited set of road segments, our approach balances the load of communication paths over the whole urban road segments, with the objective to prevent, whenever possible, local congestions in VANETs; and (2) a Software Defined Networking (SDN) based approach to monitor real-time VANETs connectivity and transmission delays on each road segment. The monitoring data is used as input to the routing approach

On The Security of Wide Area Measurement System and Phasor Data Collection

Smart grid is a typical cyber-physical system that presents the dependence of power system operations on cyber infrastructure for control, monitoring, and protection purposes. The rapid deployment of phasor measurements in smart grid transmission system has opened opportunities to utilize new applications and enhance the grid operations. Thus, the smart grid has become more dependent on communication and information technologies such as Wide Area Measurement Systems (WAMS). WAMS are used to collect real-time measurements from different sensors such as Phasor Measurement Units (PMUs) installed across widely dispersed areas. Such system will improve real-time monitoring and control; however, recent studies have pointed out that the use of WAMS introduces significant vulnerabilities to cyber-attacks that can be leveraged by attackers. Therefore, preventing or reducing the damage of cyber attacks onWAMS is critical to the security of the smart grid. In this thesis, we focus our attention on the relation between WAMS security and the IP routing protocol, which is an essential aspect to the collection of sensors measurements. Synchrophasor measurements from different PMUs are transferred through a data network and collected at one or multiple data concentrators. The timely collection of phasors from PMU dispersed across the grid allows to maintain system observability and take corrective actions when needed. This collection is made possible through Phasor Data Concentrators (PDCs) that time-align and aggregate phasor measurements, and forward the resulting stream to be used by monitoring and control applications. WAMS applications relying on these measurements have strict and stringent delay requirements, e.g., end-to-end delay as well as delay variation between measurements from different PMUs. Measurements arriving past a predetermined time period at a data concentrator will be dropped, causing incompleteness of data and affecting WAMS applications and hence the system’s operations. It has been shown that non-functional properties, such as data delay and packet drops, have a negative impact on the system functionality. We show that simply forwarding measurements from PMUs through shortest routes to phasor data collectors may result in data being dropped at their destinations. We believe therefore that there is a strong interplay between the routing paths (delays along the paths) for gathering the measurements and the value of timeout period. This is particularly troubling when a malicious attacker deliberately causes delays on some communication links along the shortest routes. Therefore, we present a mathematical model for constructing forwarding trees for PMUs’ measurements which satisfy the end to end delay as well as the delay variation requirements of WAMS applications at data concentrators. We show that a simple shortest path routing will result in larger fraction of data drop and that our method will find a suitable solution. Then, we study the relation between cyber-attack propagation and IP multicast routing. To this extent, we formulate the problem as the construction of a multicast tree that minimizes the propagation of cyber-attacks while satisfying real-time and capacity requirements. The proposed attack propagation multicast tree is evaluated using different IEEE test systems. Finally, cyber-attacks resulting in the disconnection of PDC(s) from WAMS initiate a loss of its phasor stream and incompleteness in the observability of the power system. Recovery strategies based on the re-routing of lost phasors to other connected and available PDCs need to be designed while considering the functional requirements of WAMS. We formulate a recovery strategy from loss of compromised or failed PDC(s) in the WAMS network based on the rerouting of disconnected PMUs to functional PDCs. The proposed approach is mathematically formulated as a linear program and tested on standard IEEE test systems. These problems will be extensively studied throughout this thesis