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A multipath routing strategy to prevent flooding disruption attacks in link state routing protocols for MANETs

Multipath routing has been proposed to increase resilience against network failures or improve security in Mobile Ad Hoc Networks (MANETs). The Optimized Link State Routing (OLSR) protocol has been adopted by several multipath routing strategies. They implement Multipoint Relay (MPR) nodes as a flooding mechanism for distributing control information. Ideally, the construction of multiple disjoint paths helps to increase resilience against network failures or malicious attacks. However, this is not always possible. In OLSR networks, partial link-state information is generated and flooded exclusively by the MPRs. Therefore, the nodes only obtain a partial view of the network topology. Additionally, flooding disruption attacks may affect either the selection of the MPRs or the propagation of control traffic information. As a consequence, the chances of constructing multiple disjoint paths are reduced. We present a strategy to compute multiple strictly disjoint paths between any two nodes in OLSR-based networks. We provide mechanisms to improve the view of the network topology by the nodes, as well as handling potential flooding disruption attacks to the multipath construction mechanism in OLSR-based networks. We conduct simulations that confirm our claims.

Mitigation of topology control traffic attacks in OLSR networks

The core of the Optimized Link State Routing (OLSR) protocol is the selection of Multipoint Relays (MPRs) as a flooding mechanism for distributing control traffic messages. A node in an OLSR network, selects its MPR set such that all two-hop neighbors are reachable through, at least, one MPR. However, if an MPR misbehaves during the execution of the protocol, the connectivity of the network is compromised. Additional coverage in the selection of the MPRs helps to mitigate the effect of control traffic attacks. RFC3626 defines the selection of MPRs with additional coverage. Nevertheless, the overhead of the network increases due to the added number of control traffic messages. In this paper, we propose an improved MPR selection with additional coverage. Every node selects, if it is possible, k + 1 disjoint MPR sets. The union of those sets, is a k-robust-MPR set. Thus, given a node, alternative paths are created to reach any destination two-hops away. We test both approaches against two kinds of adversaries misbehaving during the execution of the protocol. Our proposed MPR selection with additional coverage mitigates the effect of control traffic attacks by offering equivalent protection compared to the MPR selection with extra coverage presented in RFC3626, but reducing the overhead generated by redundant control information.

A new analysis of the cognitive radio jump-stay algorithm under the asymmetric model

Under use of the regulated radio spectrum is being addressed using a cognitive radio network approach termed dynamic spectrum access. Primary users have priority over the regulated radio spectrum. Secondary users may use the residual air time. We focus on the problem of meeting on a common channel by a group of secondary users. Under the asymmetric model, the secondary users have different sets of available channels. If the sets are not disjoint, they can eventually make rendezvous. The goal is to make the secondary users rendezvous on a common channel in a minimum amount of time. The jump-stay rendezvous algorithm has been created by Lin et al. to solve this problem. We develop a new analysis for the two-user expected time to rendezvous in the jump-stay rendezvous algorithm, under the asymmetric model, that better reflects its performance.

Simulation of underwater communications with a colored noise approximation and mobility

We study the software simulation of physical properties of underwater communications, namely, underwater acoustic waves and (de)modulation of underwater acoustic digital data signals. We take into account the mobility of nodes, present in underwater sensor networks. We also consider the integration with protocol layers above the physical layer, i.e., the link and network layers. In this context, mobility is relevant because there are underwater vehicles and environmental conditions causing displacements of sensors. Attenuation is sensitive to transmitter-receiver separation distance. Because of mobility, this separation distances is variable. Our simulation approach is based on the work of Borrowski (2010). The physical layer is modeled as MATLAB functions. As a function of distance and frequency, the model takes into account attenuation, noise and their effects on a phase-shift keying signal. We use OMNeT++ to model link and network layer protocols. The MATLAB functions and OMNet++ models are linked together. While MATLAB does particularly well with signal processing, OMNeT++ addresses better the protocols placed in the link layer and above.

Location-free link state routing for underwater acoustic sensor networks

We propose a location-free link state routing protocol for Underwater Acoustic Sensor Networks (UASNs). Additionally, we present the mathematical background for the theoretical capacity and transmission power metrics of an underwater acoustic channel. UASNs are formed by devices enabled with acoustic communication capabilities that are deployed underwater to perform collaborative monitoring tasks. Information is collected by a sink at the surface also equipped with a radio. The underwater communication channel is characterized by a limited bandwidth and high propagation delay. The network topology constantly changes due to mobility of the nodes. In our routing protocol, every node ranks the quality of the path that it offers toward the sink. Packet forwarding is performed hop-by-hop considering one or several routing metrics, e.g., hop count or pressure. To avoid communication void problems, every node selects a one-hop neighbor within an area that guarantees progress toward a sink. Our strategy is loop-free. It includes a recovery mode handling network topology changes. Our routing protocol was implemented in NS-3 to conduct experiments.

Security Issues in Link State Routing Protocols for MANETs

In link state routing networks, every node has to construct a topological map through the generation and exchange of routing information. Nevertheless, if a node misbehaves then the connectivity in the network is compromised. The proactive Optimized Link State Routing (OLSR) protocol has been designed exclusively for Mobile Ad Hoc Networks (MANETs). The core of the protocol is the selection of Multipoint Relays (MPRs) as an improved flooding mechanism for distributing link state information. This mechanism limits the size and number of control traffic messages. As for several other routing protocols for MANETs, OLSR does not include security measures in its original design. Besides, OLSR has been extended to address a number of problems in MANETs. For example, Hierarchical OLSR (HOLSR) has been proposed to address scalability and Multipath OLSR (MP-OLSR) to address fault tolerance. However, these OLSR extensions can be affected either by inheriting or adding new security threats. In this chapter, we present a review of security issues and countermeasures in link state routing protocols for MANETs.

Mitigation of Flooding Disruption Attacks in Hierarchical OLSR Networks

The Hierarchical Optimized Link State Routing (HOLSR) protocol was designed to improve scalability of heterogeneous Mobile Ad-Hoc Networks (MANETs). HOLSR is derived from the OLSR protocol and implements Multipoint Relay (MPR) nodes as a flooding mechanism for distributing control information. Unlike OLSR, nodes are organized in clusters and implement Hierarchical Topology Control (HTC) messages for inter-cluster communications. Nevertheless, HOLSR was designed without security measures. Therefore, a misbehaving node can affect the topology map acquisition process by interrupting the flooding of control information or disturbing the MPR selection process. We present a taxonomy of flooding disruption attacks, that affect the topology map acquisition process in HOLSR networks, and preventive mechanisms to mitigate the effect of this kind of attacks.

A new analytic model for the cognitive radio jump-stay algorithm

In cognitive radio networks, primary users have priority over the regulated radio spectrum. Secondary users may use residual air time. We focus on the problem of meeting on a common channel by a group of secondary users. The goal is to make the users rendezvous on a common channel in a minimum amount of time. The jump-stay algorithm has been created by Lin et al. to solve this problem. We construct a new analytic model for the two-user expected time to rendezvous in the jump-stay algorithm that better reflects its performance. For the sake of comparison, we also evaluate the performance of the jump-stay algorithm through simulation.

Preventing the cluster formation attack against the hierarchical OLSR protocol

The Hierarchical Optimized Link State Routing (HOLSR) protocol enhances the scalability and heterogeneity of traditional OLSR-based Mobile Ad-Hoc Networks (MANETs). It organizes the network in logical levels and nodes in clusters. In every cluster, it implements the mechanisms and algorithms of the original OLSR to generate and to distribute control traffic information. However, the HOLSR protocol was designed with no security in mind. Indeed, it both inherits, from OLSR, and adds new security threats. For instance, the existence of misbehaving nodes can highly affect important HOLSR operations, such as the cluster formation. Cluster IDentification (CID) messages are implemented to organize a HOLSR network in clusters. In every message, the hop count field indicates to the receiver the distance in hops to the originator. An attacker may maliciously alter the hop count field. As a consequence, a receiver node may join a cluster head farther away than it appears. Then, the scalability properties in a HOLSR network is affected by an unbalanced distribution of nodes per cluster. We present a solution based on the use of hash chains to protect mutable fields in CID messages. As a consequence, when a misbehaving node alters the hop count field in a CID message, the receiver nodes are able of detecting and discarding the invalid message.

Channel selection using a multiple radio model

How can a group of distributed secondary users make rendezvous on one among a set of available channels, whose exact content is a priori unknown to the participants? Let us assume that secondary users scan the set of channels, attempting to make rendezvous with each other. Each user has several radios that are concurrently used to achieve rendezvous. We propose two rendezvous algorithms for users equipped with several radios each. We study in detail the multiple user case and the asymmetric case, where the users have different but overlapping channel sets. The performance of the algorithms are analyzed and evaluated through simulation. Equations modeling the worst case performance and expected performance are developed. Graphical abstractWith the 2k-point algorithm, each user randomly and independently selects a start channel. In the example, there are two users and each user has two radios (top part of the picture). Start channel of User 1 is 0. Start channel of User 2 is 2. One radio cyclically scans channels clockwise, while the other radio cyclically scans channels counter clockwise. Scanning is performed until rendezvous is achieved by the two users, that is they are tuned to the same channel for any radio pair, in this example first radio of User 1 and second radio of User 2 (bottom part of the picture). Rendezvous is made in channel 1.Display Omitted HighlightsWe propose two rendezvous algorithms for users equipped with several radios.We study in detail the multiple user case and the case where the users have different channel sets.The performance of the algorithms are analyzed and evaluated through simulation.Equations modeling the worst case performance and expected performance are developed.