Robustness Analysis and Enhancement of MANETs Using Human Mobility Traces

Understanding network behavior that undergoes challenges is essential to constructing a resilient and survivable network. Due to the mobility and wireless channel properties, it is more difficult to model and analyze mobile ad hoc networks under various challenges. In this paper, we provide a model to assess the vulnerability of mobile ad hoc networks in face of malicious attacks. We analyze comprehensive graph-theoretical properties and network performance of the dynamic networks under attacks against the critical nodes using real-world mobility traces. Motivated by minimum spanning tree and small-world networks, we propose a network enhancement strategy by adding long-range links. We compare the performance of different enhancement strategies by evaluating a list of robustness measures. Our study provides insights into the design and construction of resilient and survivable mobile ad hoc networks.     

Comparing Restoration Concepts Using Optimal Network Configurations with Integrated Hardware and Routing Decisions

We investigate the impact of link and path restoration on the cost of telecommunication networks. The main observation is that the cost of an optimal network configuration is almost independent of the restoration concept if (i) the installation of network elements (ADMs, DXCs, or routers) and interface cards, (ii) link capacities, and (iii) working and restoration routings are simultaneously optimized.We present a mixed-integer programming model which integrates all these decisions. Using a branch-and-cut algorithm (with column generation to deal with all admissible routing paths), we solve structurally different real-world based problem instances and show that the cost of optimal solutions is almost independent of the used restoration concept.In addition, we optimize spare capacities based on predetermined shortest working paths with respect to different link weights. On our test instances, the additional cost of solutions obtained with this sequential approach, compared to simultaneous optimization of working and restoration routings, varies between 0 and 164%.Sebastian Orlowski has studied mathematics at the Technical University of Berlin, Germany. Since June 2003, he has been a research assistant at the Zuse Institute Berlin (ZIB), where he works on the design of cost-efficient telecommunication networks under survivability constraints. The current focus of his research within the DFG Research Center MATHEON is multi-layer network planning.Roland Wessäly graduated from the Technical University of Berlin with a Masters Degree in Computer Science. Since 1994 he has been a member of the optimization group at the Zuse Institute Berlin (ZIB). He developed optimization methods for the design of survivable capacitated telecommunication networks as part of his PhD Thesis in Mathematics (finished in April 2000). In 2001 he received the Vodafone Innovations award for his scientific work on network design. Since 2000 he has been managing director of the ZIB spin-off atesio GmbH, a company specialized on planning and optimization algorithms for telecommunication network operators.     

A new approach for designing fault-tolerant WDM networks

In recent years, path protection has emerged as a widely accepted technique for designing survivable WDM networks. This approach is attractive, since it is able to provide bandwidth guarantees in the presence of link failures. However, it requires allocating resources for backup lightpaths, which remain idle under normal fault-free conditions. In this paper, we introduce a new approach for designing fault-tolerant WDM networks, based on the concept of survivable routing. Survivable routing of a logical topology ensures that the lightpaths are routed in such a way that a single link failure does not disconnect the network. When a topology is generated using our approach, it is guaranteed to have a survivable routing. We further ensure that the logical topology is able to handle the entire traffic demand after any single link failure. We first present an ILP that optimally designs a survivable logical topology, and then propose a heuristic for larger networks. Experimental results demonstrate that this new approach is able to provide guaranteed bandwidth, and is much more efficient in terms of resource utilization, compared to both dedicated and shared path protection.     

Social network analytics for churn prediction in telco: Model building,evaluation and network architecture

Social network analytics methods are being used in the telecommunication industry to predict customer churn with great success. In particular it has been shown that relational learners adapted to this specific problem enhance the performance of predictive models. In the current study we benchmark different strategies for constructing a relational learner by applying them to a total of eight distinct call-detail record datasets, originating from telecommunication organizations across the world. We statistically evaluate the effect of relational classifiers and collective inference methods on the predictive power of relational learners, as well as the performance of models where relational learners are combined with traditional methods of predicting customer churn in the telecommunication industry. Finally we investigate the effect of network construction on model performance; our findings imply that the definition of edges and weights in the network does have an impact on the results of the predictive models. As a result of the study, the best configuration is a non-relational learner enriched with network variables, without collective inference, using binary weights and undirected networks. In addition, we provide guidelines on how to apply social networks analytics for churn prediction in the telecommunication industry in an optimal way, ranging from network architecture to model building and evaluation.     

New insights on survivability in multi-domain optical networks

With the development of intelligent optical networks and the general multi-protocol label switching (GMPLS) technique, the seamless convergence between IP network and optical network is no longer be a dream but a practical reality. Similar to the Internet, current optical networks have been divided into multiple domains each of which has its own network provider and management policy. Therefore, the development of multi-domain optical networks will be the trend of new-generation intelligent optical networks, and GMPLS-based survivability for multi-domain optical networks will become a hot topic of research in the future. This paper provides a comprehensive review of the existing survivable schemes in multi-domain optical networks and analyzes the shortcomings of current research. Based on previous studies, we present possible challenges and propose new ideas to design efficient survivable schemes to guide the future work of researchers in multi-domain optical networks.     

Survivable ATM mesh networks: Techniques and performance evaluation

The Capacity and Flow Assignment problem in self-healing ATM networks is an interesting one from a Generalized Multi-Protocol Label Switching (GMPLS) prospective since IP and ATM protocols are destined to co-exist together in this unified platform. This paper continues the investigation of the path-based design approach of the network survivability problem in existing ATM mesh networks. Our contribution consists in quantifying (1) the effects the selection of candidate paths per node pair has on the restoration ratio, (2) the effect of restoration schemes on the restoration ratio, (3) the effect of failure scenarios on the restoration ratio, and finally (4) the effect of network connectivity on the restoration ratio. Numerical results are presented under representative network topologies, various traffic demands and spare capacity distribution schemes. They provide additional guidelines for the design of survivable ATM mesh-type networks, from a network reliability viewpoint.     

Robustness Comparison of 15 Real Telecommunication Networks: Structural and Centrality Measurements

Multiple failures can have catastrophic consequences on the normal operation of telecommunication networks. In this sense, guaranteeing network robustness to avoid users and services being disconnected is essential. A wide range of metrics have been proposed for measuring network robustness. In this paper the taxonomy of robustness metrics in telecommunication networks has been extended and a classification of multiple failures scenarios has been made. Moreover, a structural and centrality robustness comparison of 15 real telecommunication networks experiencing multiple failures was carried out. Through this analysis the topological properties which are common for grouping networks with similar robustness are able to be identified.     

Bi-directional self-healing ring network planning

In this paper we study the network planning problem of bi-directional self-healing ring (BSHR), which is a network structure providing higher survivability when there is a failure on link or node. Given a network with nodes, links, and demand pairs, our target is to design an optimal network comprising rings, which use only the existing links to satisfy all demands. The objective is to minimize the total amount of equipment (add/drop multiplexer) on nodes, thus reducing the major cost of SHR structure. We propose two integer programming models. For larger networks, we have developed an efficient solution procedure based on its hierarchical network structure. Computational results are given to show that the solution procedure is effective in obtaining an optimal or near-optimal solution.Scope and purposeThe merging of information networking and telecommunication services has created an increasing demand for telecommunication networks of high bandwidth, aiming to exchange ever larger volumes of data in a very short time interval. The self-healing ring (SHR) is a ring network that provides redundant bandwidth in which disrupted services can be automatically restored following network failures. In this paper, we study the network planning problem of bi-directional SHR aiming to minimize the amount of equipment.     

An efficient link allocation algorithm for survivable ATM-based personal communication networks

The integration of the issue of survivability of wireless networks in the design process of the backbone network is addressed in this paper. The effectiveness of this integration plays a critical role in the success of the wireless network and the satisfaction of its mobile users. In this paper, we consider the design problem of allocating the backbone links in ATM-based personal communication networks (PCNs) that are survivable under single backbone link failures. Survivability is achieved by selecting two link-disjoint routes in the backbone network between every pair of ATM switches. We also take the novel approach of not only minimizing the diameter of the network as a primary objective but also minimizing the total length of the network as a secondary objective. We propose a new heuristic algorithm to optimize the design of the network based on both objectives. We report the results of an extensive simulation study that show that our algorithm generates backbone networks that can withstand single link failures, have shorter average diameters and smaller total lengths and achieve a higher percentage of admitted calls under a mobile environment.     

An integrated system for designing minimum cost survivabletelecommunications networks

This paper provides a Design System for obtaining minimum cost survivable telecommunications networks. It integrates heuristics for obtaining survivable topologies and improving the cost of the network with heuristics for provisioning capacity. The heuristics are based on the characteristic of the underlying graph. The Design System provides survivable telecommunications networks with 25 nodes in a matter of seconds and within 16% of a fairly relaxed lower bound     

Survivable telecommunications network design under different types of failures

Telecommunications networks are expected to provide near-instantaneous restoration in the event that some network elements fail. Models for designing survivable networks are very complex and difficult to solve optimally. In this paper, we provide simple heuristics that augment existing network resources to ensure restoration under several scenarios of a single failure. The goal is to demonstrate that effective, though not necessarily optimal, survivable designs can be achieved by augmenting capacities along prudently selected variants of spanning tree and ring structures, without resorting to complex mathematical programming methods. The first model considers line restoration (reroutes around the failed link) under a partial link failure. We propose a heuristic that augments capacities of selected network links by forming a "virtual" spanning tree of restoration capacity. The second model provides line restoration under a complete link failure. We propose a heuristic that ensures survivability by repeatedly constructing spanning trees to various subnetworks. The third model provides path restoration (end-to-end reroutes) under a node failure. We propose a heuristic that repeatedly constructs restoration rings that cover a subset of source-destination nodes that carry traffic through intermediate nodes.     

Multi-period design of survivable wireless access networks under capacity constraints

Design of survivable wireless access networks plays a key role in the overall design of a wireless network. In this research, the multi-period design of a wireless access network under capacity and survivability constraints is considered. Given the location of the cells and hubs, the cost of interconnection, and the demands generated by the cells, the goal of the designer is to find the best interconnection between cells and hubs so that the overall connection cost is minimized and the capacity and the survivability constraints are met. Integer programming formulations for this problem are proposed and the problems are solved using heuristic methods. Using different combination of network sizes, demand patterns and various time periods, a number of numerical experiments are conducted and all of them are found to yield high quality solutions.     

Uncertainty in telecommunication network design

Abstract: The design of telecommunication networks is a complex activity involving a vast amount of input data and numerous design rules. Much of the data is estimated and many of the rules are based upon experiential knowledge. The use of existing uncertainty techniques in expert systems is not really suited to the complexity of telecommunication network design. Having investigated the uncertainty problem, it is believed that a more rational method has been found for use in this application area. The paper presents the 'Uncertainty Window'technique and its testing on one aspect of network design, namely that of network synchronisation.
The essence of this uncertainty process is one of associating individual uncertainty windows with the relevant rules, data and facts of a design problem, which results in providing the network designer with an insight into the possible uncertainties within a design at each stage of the process. It indicates which information sources provide the dominant uncertainty and which assumptions are critical, needing further investigation, in order to improve the level of confidence in the overall design. The windowing technique works by virtue of its ability to retain the composition of the uncertainties within the problem and their associated values, assumptions, and so forth and allows for better solutions to be obtained.     

Datacab: a geographical-information-system-based expert system for the design of cable networks

Abstract: Telecommunication networks have evolved over time as a result of technological advances, and network topologies and equipment have become increasingly complex. Expert systems are being successfully applied to the management of telecommunication networks. However, applying expert systems to network design is another especially beneficial yet still not very common approach. In this paper we propose a rule-based expert system called Datacab. Datacab was developed at Enditel Endesa in collaboration with the Electronic Technology Department of the University of Seville, for the automatic design of hybrid fibre coax (HFC) cable networks. Using data from a geographical information system as input, it automatically generates viable HFC network designs.     

Generalized Loss Models and Queueing-loss Networks

The classical Erlang and Engset loss models have been used extensively in the traffic engineering of traditional telephone exchanges. More recently, these models have been generalized to the so-called loss networks, which provide models for resource-sharing in multi-service telecommunication networks. In this paper, we introduce a new generalized class of models, queueing-loss networks, which captures both queueing and loss aspects of a system. The queueing-loss network model is a natural extension of queueing networks and loss networks that have the product-form solution. We discuss applications of the model and analyze a particular example of a simple queueing-loss network.     

A Novel Long Term Telecommunication Network Planning Framework

The design of large scale telecommunication networks is more than the technical allocation of capacity and path routing. By examining the design and allocation of resources in a broader sense, telecommunication network planning and management can better deliver value to the various stakeholders. This is significant especially when deploying networks in economically marginal areas such are rural, remote, or economically depressed regions. This paper presents a planning framework to systematically incorporate the influences, resources and decisions to effectively build or expand a network. Using a stake holders, input, process, output, customer approach, six key areas of society that derive value from better communication infrastructure in relatively unique manners were identified. These areas include healthcare, education, business, and others. The framework presented defines the inputs and outputs that accounts for the range of influences and outcomes in a network planning process. Inputs are broken down into four areas of concern (technical, market, financial, and application trends) that can influence how a network could be designed, along with four output areas (auxiliary activities, deployment strategies, technical design, and ownership and access). Through an extensive literature survey across many industries this framework was established to incorporate the many social economic and technical factors that influence telecommunication network planning and design.     

Designing tributary networks with multiple ring families

Advances in telecommunication technology result in improved service, but can also lead to difficult and challenging network design problems. For example, networks in which nodes are connected by rings of optical fiber can now be used to provide rapid service restoration in the event of a failure. However, as a result, network designers are faced with the new problem of designing networks based on topological ring structures. In this paper, we consider the particular case of tributary network design. In a tributary network, a group of nodes are connected to a hub node, which is used as a point of interconnection with other parts of the network. For a particular network architecture, we describe an algorithm to determine how many topological ring structures are required, and which nodes should be included on each. We highlight connections between this problem and problems in vehicle routing.A common architecture for a telecommunications network consists of several tributary (often called access) networks, which connect locations to hubs, and a backbone network, which interconnects the hubs. This paper describes a heuristic approach for designing tributary networks based on self-healing rings (SHRs). The tributary network consists of multiple ring families, and each of those is comprised of one or more SHRs, called “stacked” rings. The SHRs in a given ring family are routed over the same cycle of optical fiber cables, but each SHR serves only a subset of the locations along the cycle. Each demand location is assigned to a single SHR on one of the ring families, whereas the hub is assigned to all SHRs on all ring families. A link that is used by some ring family incurs a fixed cost plus a variable cost per SHR associated with that family. Each SHR is constrained by the demand volume it can handle and by the number of locations it can serve. This tributary ring network design problem can be viewed as a complex version of a vehicle routing problem with a single-depot andmultiple vehicles. Our algorithm is initiated with numerous ring families. It then attempts to merge these families, while ensuring that savings are realized in terms of the sum of fixed and variable costs.     

Multi-layer survivable routing mechanism in GMPLS based optical networks

The structure of IP/MPLS over optical networks has become the trend for new generation backbone transport networks since the technology of general multi-protocol label switching (GMPLS) can realize the seamless converage between IP and optical networks. At the same time, due to the high-speed transmission rate of each wavelength in optical networks, survivability is a very important issue and has been studied all through these years. Therefore, in new generation GMPLS based networks, it is very necessary to investigate the multi-layer survivable algorithms. In this paper, we comprehensively review the existing survivable algorithms in multi-layer networks and analyze the shortages of current researches. Based on previous studies, we prospect challenges and propose new solutions of designing efficient survivable algorithms to well guide the future work of researchers in multi-layer networks.     

Survivable millimeter-wave mesh networks

Millimeter-wave mesh networks have the potential to provide cost-effective high-bandwidth solutions to many current bandwidth-constrained networks including cellular backhaul. However, the availability of such networks is severely limited due to their susceptibility to weather, such as precipitation and humidity. In this paper, we present a rigorous approach to survivable millimeter-wave mesh networks based on experimentation, modeling, and simulation. Individual link performance is characterised using frame error-rate measurements from millimeter-wave transmissions on test links over a period of one year. A geometric model based on radar-reflectivity data is used to characterise rain storms and determine their impact on spatially correlated links of a mesh network. To mitigate the impact of link impairments on network services, we present two cross-layered routing protocols to route around the failures: P-WARP (predictive weather-assisted routing protocol) and XL-OSPF (cross-layered open shortest-path first). We conduct a performance analysis of the proposed mesh network under the presence of actual weather events as recorded by the US National Weather Service. Results show that the proposed approach yields the highest dependability when compared against existing routing methods.     

A multi-objective approach for solving the survivable network design problem with simultaneous unicast and anycast flows

In this paper, we consider the survivable network design problem for simultaneous unicast and anycast flow requests. We assume that the network is modeled by a connected and undirected graph. This problem aims at finding a set of connections with a minimized network cost in order to protect the network against any single failure. The cost is computed using the all capacities modular cost (ACMC) model and a set of flow demands. We name it as ACMC-based survivable network design problem (A-SNDP). It is proved that the problem is NP-hard. We introduce a multi-objective approach to solve A-SNDP. The objectives are to minimize the network cost (NCost) and the network failure (NFail). Extensive simulation results on instances of Polska, Germany and Atlanta networks showed the efficiency of the multi-objective approach for solving A-SNDP.