Status of this Memo This memo defines an Experimental Protocol for the Internet community. It does not specify an Internet standard of any kind. Discussion and suggestions for improvement are requested. Distribution of this memo is unlimited.

Most recent ad hoc network research has focused on providing routing services without considering security. In this paper, we detail security threats against ad hoc routing protocols, specifically examining AODV and DSR. In light of these threats, we identify three different environments with distinct security requirements. We propose a solution to one, the managed-open scenario where no network infrastructure is pre-deployed, but a small amount of prior security coordination is expected. Our protocol, ARAN, is based on certificates and successfully defeats all identified attacks.

One of the most important methods for evaluating the characteristics of ad hoc networking protocols is through the use of simulation. Simulation provides researchers with a number of significant benefits, including repeatable scenarios, isolation of parameters, and exploration of a variety of metrics. The topology and movement of the nodes in the simulation are key factors in the performance of the network protocol under study. Once the nodes have been initially distributed, the mobility model dictates the movement of the nodes within the network. Because the mobility of the nodes directly impacts the performance of the protocols, simulation results obtained with unrealistic movement models may not correctly reflect the true performance of the protocols. The majority of existing mobility models for ad hoc networks do not provide realistic movement scenarios; they are limited to random walk models without any obstacles. In this paper, we propose to create more realistic movement models through the incorporation of obstacles. These obstacles are utilized to both restrict node movement as well as wireless transmissions. In addition to the inclusion of obstacles, we construct movement paths using the Voronoi diagram of obstacle vertices. Nodes can then be randomly distributed across the paths, and can use shortest path route computations to destinations at randomly chosen obstacles. Simulation results show that the use of obstacles and pathways has a significant impact on the performance of ad hoc network protocols.

To date, the majority of ad hoc routing protocol research has been done using simulation only.

Abstract-Initial work in ad hoc routing has considered only the problem of providing efficient mechanisms for finding paths in very dynamic networks, without considering security. Because of this, there are a number of attacks that can be used to manipulate the routing in an ad hoc network. In this paper, we describe these threats, specifically showing their effects on AODV and DSR. Our protocol, named Authenticated Routing for Ad hoc Networks (ARAN), uses public-key cryptographic mechanisms to defeat all identified attacks. We detail how ARAN can secure routing in environments where nodes are authorized to participate but untrusted to cooperate, as well as environments where participants do not need to be authorized to participate. Through both simulation and experimentation with our publicly-available implementation, we characterize and evaluate ARAN and show that it is able to effectively and efficiently discover secure routes within an ad hoc network.

The growing popularity of wireless networks has led to cases of heavy utilization and congestion. In heavily utilized wireless networks, the wireless portion of the network is a major performance bottleneck. Understanding the behavior of the wireless portion of such networks is critical to ensure their robust operation. This understanding can also help optimize network performance. In this paper, we use link layer information collected from an operational, large-scale, and heavily utilized IEEE 802.11b wireless network deployed at the 62 nd Internet Engineering Task Force (IETF) meeting to study congestion in wireless networks. We motivate the use of channel busy-time as a direct measure of channel utilization and show how channel utilization along with network throughput and goodput can be used to define highly congested, moderately congested, and uncongested network states. Our study correlates network congestion and its effect on link-layer performance. Based on these correlations we find that (1) current rate adaptation implementations make scarce use of the 2 Mbps and 5.5 Mbps data rates, (2) the use of Request-toSend/Clear-to-Send (RTS-CTS) prevents nodes from gaining fair access to a heavily congested channel, and (3) the use of rate adaptation, as a response to congestion, is detrimental to network performance.

Abstract. The incredible growth in the capabilities and functionality of mobile devices has enabled new applications to emerge. Due to the potential for node mobility, along with significant node heterogeneity, characteristics such as very large delays, intermittent links and high link error rates pose a new set of challenges. Along with these challenges, end-to-end paths are assumed not to exist and message relay approaches are often adopted. While message flooding happens to be a simple and robust solution for such cases, its cost in terms of network resource consumption is unaffordable. In this paper, we focus on the evaluation of different controlled message flooding schemes over large-scale, sparse mobile networks. We study the effect of these schemes on message delay and network resource consumption. Our simulations show that our schemes can save substantial network resources while incurring a negligible increase in the message delivery delay.

INTRODUCTIONInfrastructured IEEE 802.11b networks are becoming ubiquitous. These networks offer high bandwidth wireless connectivity well-suited for a variety of traffic types, including multimedia distribution. One drawback of infrastructured networks is the complexity of deploying and configuring these networks. Ad hoc networking protocols do not suffer from this limitation. By using a multihop ad hoc network connectivity is maximized.For quality multimedia sessions, routing paths between nodes in an ad hoc network must be continually monitored. Numerous ad hoc routing protocols [1,3,4,7,12] make use of periodic broadcast messages to determine local connectivity. Also, because of the difficulty of obtaining IEEE 802.11 feedback about link connectivity in real networks, many current protocol implementations utilize hello messages [2,3,6,9,10].The basis of using hello messages to determine connectivity stems from the assumption that reception of a hello message indicates a viable communication channel with the source of the hello. This mechanism works well on wired networks, which experience few packet losses and connectivity changes. However, when used in wireless ad hoc networks the effectiveness decreases due to many factors. Some of the factors that have significant effect are: hello loss settings, hello packet size and 802.11b packet handling.