Fast emergency paths schema to overcome transient link failures in ospf routing

A reliable network infrastructure must be able to sustain traffic flows, even when a failure occurs and changes the network topology. During the occurrence of a failure, routing protocols, like OSPF, take from hundreds of milliseconds to various seconds in order to converge. During this convergence period, packets might traverse a longer path or even a loop. An even worse transient behaviour is that packets are dropped even though destinations are reachable. In this context, this paper describes a proactive fast rerouting approach, named Fast Emergency Paths Schema (FEP-S), to overcome problems originating from transient link failures in OSPF routing. Extensive experiments were done using several network topologies with different dimensionality degrees. Results show that the recovery paths, obtained by FEPS, are shorter than those from other rerouting approaches and can improve the network reliability by reducing the packet loss rate during the routing protocols convergence caused by a failure.Comment: 18 page

Improving VANETs Connectivity with a Totally Ad Hoc Living Mobile Backbone

The vehicular ad hoc network (VANET) for intelligent transportation systems is an emerging concept to improve transportation security, reliability, and management. The network behavior can be totally different in topological aspects because of the mobility of vehicular nodes. The topology can be fully connected when the flow of vehicles is high and may have low connectivity or be invalid when the flow of vehicles is low or unbalanced. In big cities, the metropolitan buses that travel on exclusive lanes may be used to set up a metropolitan vehicular data network (backbone), raising the connectivity among the vehicles. Therefore, this paper proposes the implementation of a living mobile backbone, totally ad hoc (MOB-NET), which will provide infrastructure and raise the network connectivity. In order to show the viability of MOB-NET, statistical analyses were made with real data of express buses that travel through exclusive lanes, besides evaluations through simulations and analytic models. The statistic, analytic, and simulation results prove that the buses that travel through exclusive lanes can be used to build a communication network totally ad hoc and provide connectivity in more than 99% of the time, besides raising the delivery rate up to 95%

Routing in Vehicular Ad Hoc Networks: Main Characteristics and Tendencies

The message routing in vehicular ad hoc networks (VANETs) is an attractive and promising area for research. These networks do not have a central coordination, the nodes are mobile, and the topology is highly dynamic, making the routing process a big challenge, since it is responsible for ensuring message delivery with small overhead and delay. In the literature, there are several routing protocols that can be used in VANETs; in this way, the main objective of this work is to classify, discuss, and compare such protocols through a review of research in this field. The protocol classification is based on the following criteria: type of architecture and mode of operation. Moreover, this work emphasizes the potential of the application of bioinspired and bus-based techniques in the routing problem solutions, which has been revealed as a main tendency nowadays. Bioinspired routing protocols are based on the behavior of entities in the nature, and they are meant to work in a distributed mode, using mobile agents to find routes with specific features. In a parallel line of research, the differentiated behavior of urban transport vehicles suggests that a system that makes use of buses to create a communication infrastructure can perform better when compared to a system that does not distinguish between vehicles

Improving VANETs Connectivity with a Totally Ad Hoc Living Mobile Backbone

The vehicular ad hoc network (VANET) for intelligent transportation systems is an emerging concept to improve transportation security, reliability, and management. The network behavior can be totally different in topological aspects because of the mobility of vehicular nodes. The topology can be fully connected when the flow of vehicles is high and may have low connectivity or be invalid when the flow of vehicles is low or unbalanced. In big cities, the metropolitan buses that travel on exclusive lanes may be used to set up a metropolitan vehicular data network (backbone), raising the connectivity among the vehicles. Therefore, this paper proposes the implementation of a living mobile backbone, totally ad hoc (MOB-NET), which will provide infrastructure and raise the network connectivity. In order to show the viability of MOB-NET, statistical analyses were made with real data of express buses that travel through exclusive lanes, besides evaluations through simulations and analytic models. The statistic, analytic, and simulation results prove that the buses that travel through exclusive lanes can be used to build a communication network totally ad hoc and provide connectivity in more than 99% of the time, besides raising the delivery rate up to 95%

IP Network Design with End-to-End QoS Constraints: The VPN Case

Abstract. The traditional approaches to optimal design and planning of packet networks focus on the networklayer infrastructure, thus neglecting end-to-end Quality of Service (e2e QoS) issues, and Service Level Agreement (SLA) guarantees. This is quite inappropriate since the Internet today carries a wide range of critical telecommunication services. The challenge in the area is how to devise reasonable packet network design methodologies that allow the choice of the most adequate set of network resources, subject to e2e QoS constraints and, at the same time, consider the traffic dynamics of today’s packet networks. In this paper we describe a simple methodology to tackle the packet network design problem, and illustrate an example of its application to the optimization of link capacities and routing in a corporate Virtual Private Network (VPN), where traffic is mostly due to TCP connections. An efficient Lagrangean relaxation based heuristic procedure is developed to find bounds and solutions for the considered problem, and numerical results for a variety of problem instances are reported