Herbert Rubens

An on-demand secure routing protocol resilient to byzantine failures

An ad hoc wireless network is an autonomous self-organizing system ofmobile nodes connected by wireless links where nodes not in directrange can communicate via intermediate nodes. A common technique usedin routing protocols for ad hoc wireless networks is to establish therouting paths on-demand, as opposed to continually maintaining acomplete routing table. A significant concern in routing is theability to function in the presence of byzantine failures whichinclude nodes that drop, modify, or mis-route packets in an attempt todisrupt the routing service.We propose an on-demand routing protocol for ad hoc wireless networks that provides resilience to byzantine failures caused by individual or colluding nodes. Our adaptive probing technique detects a malicious link after log n faults have occurred, where n is the length of the path. These links are then avoided by multiplicatively increasing their weights and by using an on-demand route discovery protocol that finds a least weight path to the destination.

High Throughput Route Selection in Multi-rate Ad Hoc Wireless Networks

Modern wireless devices, such as those that implement the 802.11b standard, utilize multiple transmission rates in order to accommodate a wide range of channel conditions. Traditional ad hoc routing protocols typically use minimum hop paths. These paths tend to contain long range links that have low effective throughput and reduced reliability in multi-rate networks. In this work, we present the Medium Time Metric (MTM), which is derived from a general theoretical model of the attainable throughput in multi-rate ad hoc wireless networks. MTM avoids using the long range links favored by shortest path routing in favor of shorter, higher throughput, more reliable links. We present NS2 simulations that show that using MTM yields an average total network throughput increase of 20% to 60%, depending on network density. In addition, by combining the MTM with a medium time fair MAC protocol, average total network throughput increases of 100% to 200% are obtained over traditional route selection and packet fairness techniques.

ODSBR: An on-demand secure Byzantine resilient routing protocol for wireless ad hoc networks

Ah hoc networks offer increased coverage by using multihop communication. This architecture makes services more vulnerable to internal attacks coming from compromised nodes that behave arbitrarily to disrupt the network, also referred to as Byzantine attacks. In this work, we examine the impact of several Byzantine attacks performed by individual or colluding attackers. We propose ODSBR, the first on-demand routing protocol for ad hoc wireless networks that provides resilience to Byzantine attacks caused by individual or colluding nodes. The protocol uses an adaptive probing technique that detects a malicious link after log n faults have occurred, where n is the length of the path. Problematic links are avoided by using a route discovery mechanism that relies on a new metric that captures adversarial behavior. Our protocol never partitions the network and bounds the amount of damage caused by attackers. We demonstrate through simulations ODSBRs effectiveness in mitigating Byzantine attacks. Our analysis of the impact of these attacks versus the adversarys effort gives insights into their relative strengths, their interaction, and their importance when designing multihop wireless routing protocols.

The medium time metric: high throughput route selection in multi-rate ad hoc wireless networks

Modern wireless devices, such as those that implement the 802.11abg standards, utilize multiple transmission rates in order to accommodate a wide range of channel conditions. The use of multiple rates presents a significantly more complex challenge to ad hoc routing protocols than the traditional single rate model. The hop count routing metric, which is traditionally used in single rate networks, is sub-optimal in multi-rate networks as it tends to select short paths composed of maximum length links. In a multi-rate network, these long distance links operate at the slowest available rate, thus achieving low effective throughput and reduced reliability due to the low signal levels. In this work we explore the lower level medium access control and physical phenomena that affect routing decisions in multi-rate ad hoc networks. We provide simulation results which illustrate the impact of these phenomena on effective throughput and show how the traditional minimum hop routing strategy is inappropriate for multi-rate networks. As an alternative, we present the Medium Time Metric (MTM) which avoids using the long range links often selected by shortest path routing in favor of shorter, higher throughput, more reliable links. Our experimental results with 802.11 g radios show that the Medium Time Metric achieves significantly higher throughput then alternative metrics. We observed up to 17 times more end-to-end TCP throughput than when the Min Hop or ETX metrics were used.

On the Survivability of Routing Protocols in Ad Hoc Wireless Networks

Survivable routing protocols are able to provide service in the presence of attacks and failures. The strongest attacks that protocols can experience are attacks where adversaries have full control of a number of authenticated nodes that behave arbitrarily to disrupt the network, also referred to as Byzantine attacks. This work examines the survivability of ad hoc wireless routing protocols in the presence of several Byzantine attacks: black holes, flood rushing, wormholes and overlay network wormholes. Traditional secure routing protocols that assume authenticated nodes can always be trusted, fail to defend against such attacks. Our protocol, ODSBR, is an on-demand wireless routing protocol able to provide correct service in the presence of failures and Byzantine attacks. We demonstrate through simulation its effectiveness in mitigating such attacks. Our analysis of the impact of these attacks versus the adversary’s effort gives insights into their relative strengths, their interaction and their importance when designing wireless routing protocols.

The pulse protocol: energy efficient infrastructure access

We present the pulse protocol which is designed for multi-hop wireless infrastructure access. While similar to the more traditional access point model, it is extended to operate across multiple hops. This is particularly useful for conference, airport, or large corporate deployments. In these types of environments where users are highly mobile, energy efficiency becomes of great importance. The pulse protocol utilizes a periodic flood initiated at the network gateways which provides both routing and synchronization to the network. This synchronization is used to allow idle nodes to power off their radios for a large percentage of the time when they are not needed for packet forwarding. This results in substantial energy savings. Through simulation we validate the performance of the routing protocol with respect to both packet delivery and energy savings.

Provably competitive adaptive routing

An ad hoc wireless network is an autonomous self-organizing system of mobile nodes connected by wireless links where nodes not in direct range communicate via intermediary nodes. Routing in ad hoc networks is a challenging problem as a result of highly dynamic topology as well as bandwidth and energy constraints. In addition, security is critical in these networks due to the accessibility of the shared wireless medium and the cooperative nature of ad hoc networks. However, none of the existing routing algorithms can withstand a dynamic proactive adversarial attack. The routing protocol presented in this work attempts to provide throughput-competitive route selection against an adaptive adversary. A proof of the convergence time of our algorithm is presented as well as preliminary simulation results.

The pulse protocol: sensor network routing and power saving

We present a performance evaluation of the pulse protocol operating in a sensor network. In this work, a number of modifications are made to the original pulse protocol to provide efficient operation in a sensor network environment. The pulse protocol utilizes a periodic flood (the pulse) initiated by a single node (the pulse source) to provide both routing and synchronization to the network. This periodic pulse forms a pro-actively updated spanning tree rooted at the pulse source. Nodes communicate by forwarding packets through this tree. In addition, nodes are able to synchronize with the periodic pulse, allowing idle nodes to power off their radios a large percentage of the time when they are not required for packet forwarding. This results in substantial energy savings. A new mechanism called intermediate wake-up periods is introduced in this work in order to reduce the energy costs of low delay applications. Through simulation we explore the performance of both the protocol and the modifications with respect to energy efficiency and delay.

Beacon-Based Routing for Tactical Networks

The U.S. Department of Defenses (DoD) warfighter is reliant upon the development of a reliable, resilient communications capability under harsh, battlefield environments. Due to high mobilities and the nature of the various terrains, the dynamics of the communications links is extremely erratic and rapidly changing. This results in extreme strain on the performance of routing protocols attempting to find and maintain viable communications paths. In this paper we discuss and analyze a new class of routing protocols which we refer to as Beacon-Based Routing protocols. Beacon-Based Routing protocols proactivity build a small number of, typically one or two, spanning trees in the network and use these trees to discover paths on demand. The existence of one (or more) spanning tree(s) ensures full network connectivity and hence can be used to find network paths without the need for network-wide broadcast of discovery messages, as in other on-demand routing protocols. This class of routing protocols represents the generalization of the Pulse Protocol [1], originally developed in 2002 for applications to Internet access networks. The performance of the Pulse Protocol was analyzed in [1] and [2] in various applications including general Mobile Ad-Hoc Networks (MANETs) and in sensor networks. As we discuss in this paper, the Beacon-Based Routing protocol class has optimal behavior with respect to the communications overhead required to run the protocol. As such, its scaling behavior is superior to other existing routing protocol classes when assessed in the context of a MANET.

Swarm intelligence routing resilient to byzantine adversaries

An ad hoc wireless network is an autonomous self-organizing system of mobile nodes connected by wireless links where nodes not in direct range communicate via intermediary nodes. Routing in ad hoc networks is a challenging problem as a result of highly dynamic topology as well as bandwidth and energy constraints. The Swarm intelligence paradigm has recently demonstrated as an effective approach for routing in small network configurations with no adversarial intervention. These algorithms have also been proven to be robust and resilient to changes in node configuration. However, none of the existing routing algorithms can withstand a dynamic proactive adversarial attack, where the network may be completely controlled by byzantine adversaries. The routing protocol presented in this work attempts to provide throughput competitive route selection against an adversary which is essentially unlimited; more specifically, the adversary benefits from complete collusion of adversarial nodes, can engage in arbitrary byzantine behavior and can mount arbitrary selective adaptive attacks, dynamically changing its attack with each new packet. In this work, we show how to use the Swarm intelligence paradigm and distributed reinforcement learning in order to develop provably secure routing against byzantine adversaries. Preliminary simulation results are presented.