Performance Analysis of Dynamic Routing Protocols in a Low Earth Orbit Satellite Data Network

Modern warfare is placing an increasing reliance on global communications. Currently under development are several Low Earth Orbit (LEO) satellite systems that propose to deliver voice and data traffic to subscribers anywhere on the globe. However, very little is known about the performance of conventional routing protocols under orbital conditions where the topology changes on a scale of minutes rather than days. This thesis compares two routing protocols in a LEO environment. One (Extended Bellman-Ford) is a conventional terrestrial routing protocol, while the other (Darting) is a new protocol which has been proposed as suitable for use in LEO networks. These protocols are compared via computer simulation in two of the proposed LEO systems (Globalstar and Iridium), under various traffic intensities. Comparative measures of packet delay, convergence speed, and protocol overhead are made It was found both protocols were roughly equivalent in end-to-end delay characteristics, though the Darting protocol had a much higher overhead load and demonstrated higher instability at network update periods. For example, while steady state end-to-end delays were within a few milliseconds, in one case Darting showed an increase of 764% in convergence time over Extended Bellman-Ford with an increase of 149% in overhead. Over all cases, Darting required an average of 72.1% more overhead than Extended Bellman-Ford to perform the same work. Darting was handicapped by its strong correlation between data traffic and protocol overhead. Modifications to reduce this overhead would result in much closer performance

Study of Routing Protocols in Telecommunication Networks

In this paper we have discussed the problem of routing in telecommunication networks and the salient characteristics of some of the most popular routing schemes. In particular, we have discussed the characteristics of adaptive and multipath routing solutions versus static and single-path strategies

Reinforcing Reachable Routes

This paper studies the evaluation of routing algorithms from the perspective of reachability routing, where the goal is to determine all paths between a sender and a receiver. Reachability routing is becoming relevant with the changing dynamics of the Internet and the emergence of low-bandwidth wireless/ad-hoc networks. We make the case for reinforcement learning as the framework of choice to realize reachability routing, within the confines of the current Internet infrastructure. The setting of the reinforcement learning problem offers several advantages,including loop resolution, multi-path forwarding capability, cost-sensitive routing, and minimizing state overhead, while maintaining the incremental spirit of current backbone routing algorithms. We identify research issues in reinforcement learning applied to the reachability routing problem to achieve a fluid and robust backbone routing framework. This paper also presents the design, implementation and evaluation of a new reachability routing algorithm that uses a model-based approach to achieve cost-sensitive multi-path forwarding; performance assessment of the algorithm in various troublesome topologies shows consistently superior performance over classical reinforcement learning algorithms. The paper is targeted toward practitioners seeking to implement a reachability routing algorithm

Multipath policy routing in packet switched networks

Dissertação apresentada para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores, pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaNowadays, the continuous operations of large networks, under multiple ownerships, are of tremendous importance and as a result, routing protocols have gained numerous extensions and accumulated complexity. Policy-based routing can be of signi cance for common networks when the cost of transporting a bit is no longer the biggest pressure point. The best path problem is a generalization of the shortest path problem that suits policy based routing. This means that preferences for the paths depend on semantically rich characteristics, in which two di erent paths may have the same preference. However, current policy-based routing models cannot take full advantage of the multiplicity of connections to a given destination and are single path in nature. Therefore multipath can bring several advantages in policy based routing. Designing multipath routing protocols based on policies seem to be a problem of interest. To model routing problems, algebraic structures and graph theory are used. Through variants of classical methods of linear algebra routing problems can be solved. The objective of this dissertation is to devise a multipath policy-based routing protocol using a simple destination-based hop-by-hop protocol with independent forwarding decisions. Networks featuring these characteristics can be more resilient to failures, provide better tra c distribution and maintain a simple forwarding paradigm. The dissertation concludes with the trade-o 's between the exibility of the proposed solution, the amount of multiple paths that can be used simultaneously and the network restrictions that must be applied

Study and Analysis of Ant System

Alot of species of ants have a trail-laying/trailfollowing behavior when foraging. While moving, individual ants deposit on the ground a volatile chemical substance called pheromone, forming in this way pheromone trails. Ants can smell pheromone and, when choosing their way, they tend to choose, in probability, the paths marked by stronger pheromone concentrations. In this way they create a sort of attractive potential field, the pheromone trails allows the ants to find their way back to food sources (or to the nest). Also, they can be used by other ants to find the location of the food sources discovered by their nest mates

FRAMEWORK FOR AD HOC NETWORK COMMUNICATION IN MULTI-ROBOT SYSTEMS

Assume a team of mobile robots operating in environments where no communication infrastructure like routers or access points is available. The robots have to create a mobile ad hoc network, in that case, it provides communication on peer-to-peer basis. The paper gives an overview of existing solutions how to route messages in such ad hoc networks between robots that are not directly connected and introduces a design of a software framework for realization of such communication. Feasibility of the proposed framework is shown on the example of distributed multi-robot exploration of an a priori unknown environment. Testing of developed functionality in an exploration scenario is based on results of several experiments with various input conditions of the exploration process and various sizes of a team and is described herein