Analysis of Multipoint Relays Selection in the OLSR Routing Protocol with and without QoS Support

Mobile ad hoc networks have very attractive intrinsic qualities. However they will be adopted only if they are able to support applications with QoS requirements. They must provide a route providing the QoS requested by a flow. The OLSR routing protocol can be extended for that purpose. OLSR relies on multipoint relay (MPR) selection that has an important effect on the routing protocol's performances. Indeed, the overhead generated by the OLSR protocol and more particularly the flooding efficiency depend on MPR selection. Moreover, MPRs are used as intermediate nodes in the routes. The analysis of MPR selection presented in this report gives quantitative results and also takes into consideration QoS support. Simulations on large and dense networks show that our analysis is highly accurate

Trust-based security for the OLSR routing protocol

International audienceThe trust is always present implicitly in the protocols based on cooperation, in particular, between the entities involved in routing operations in Ad hoc networks. Indeed, as the wireless range of such nodes is limited, the nodes mutually cooperate with their neighbors in order to extend the remote nodes and the entire network. In our work, we are interested by trust as security solution for OLSR protocol. This approach fits particularly with characteristics of ad hoc networks. Moreover, the explicit trust management allows entities to reason with and about trust, and to take decisions regarding other entities. In this paper, we detail the techniques and the contributions in trust-based security in OLSR. We present trust-based analysis of the OLSR protocol using trust specification language, and we show how trust-based reasoning can allow each node to evaluate the behavior of the other nodes. After the detection of misbehaving nodes, we propose solutions of prevention and countermeasures to resolve the situations of inconsistency, and counter the malicious nodes. We demonstrate the effectiveness of our solution taking different simulated attacks scenarios. Our approach brings few modifications and is still compatible with the bare OLSR

An analysis of the lifetime of OLSR networks

The Optimized Link State Routing (OLSR) protocol is a well-known route discovery protocol for ad-hoc networks. OLSR optimizes the flooding of link state information through the network using multipoint relays (MPRs). Only nodes selected as MPRs are responsible for forwarding control traffic. Many research papers aim to optimize the selection of MPRs with a specific purpose in mind: e.g., to minimize their number, to keep paths with high Quality of Service or to maximize the network lifetime (the time until the first node runs out of energy). In such analyzes often the effects of the network structure on the MPR selection are not taken into account. In this paper we show that the structure of the network can have a large impact on the MPR selection. In highly regular structures (such as grids) there is even no variation in the MPR sets that result from various MPR selection mechanisms. Furthermore, we study the influence of the network structure on the network lifetime problem in a setting where at regular intervals messages are broadcasted using MPRs. We introduce the ’maximum forcedness ratio’, as a key parameter of the network to describe how much variation there is in the lifetime results of various MPR selection heuristics. Although we focus our attention to OLSR, being a widely implemented protocol, on a more abstract level our results describe the structure of connected sets dominating the 2-hop neighborhood of a node

Performance analysis of MANET routing protocols in the presence of self-similar traffic

A number of measurement studies have convincingly demonstrated that network traffic can exhibit a noticeable self-similar nature, which has a considerable impact on queuing performance. However, many routing protocols developed for MANETs over the past few years have been primarily designed and analyzed under the assumptions of either CBR or Poisson traffic models, which are inherently unable to capture traffic self-similarity. It is crucial to re-examine the performance properties of MANETs in the context of more realistic traffic models before practical implementation show their potential performance limitations. In an effort towards this end, this paper evaluates the performance of three well-known and widely investigated MANET routing protocols, notably DSR, AODV and OLSR, in the presence of the bursty self-similar traffic. Different performance aspects are investigated including, delivery ratio, routing overhead, throughput and end-to-end delay. Our simulation results indicate that DSR routing protocol performs well with bursty traffic models compared to AODV and OLSR in terms of delivery ratio, throughput and end-to-end delay. On the other hand, OLSR performed poorly in the presence of self-similar traffic at high mobility especially in terms of data packet delivery ratio, routing overhead and delay. As for AODV routing protocol, the results show an average performance, yet a remarkably low and stable end-to-end delay

A testbed for MANETs: Implementation, experiences and learned lessons

In this paper, we present the implementation, experiences and lessons learned of our tesbed for Ad-hoc networks and Mobile Ad hoc Networks (MANETs). We used OLSR protocol for real experimental evaluation. We investigate the effect of mobility and topology changing in the throughput of a MANET. We study the impact of best-effort traffic for Mesh Topology and Linear Topology. In this work, we consider eight experimental models and we assess the performance of our testbed in terms of throughput, round trip time and packet loss. We found that some of the OLSR's problems can be solved, for instance the routing loop, but this protocol still has the self-interference problem. Also, there is an intricate interdependence between MAC layer and routing layer. We carried out the experiments considering stationary nodes of an Ad-hoc network and the node mobility of MANETs. We found that throughput of TCP was improved by reducing Link Quality Window Size (LQWS). For TCP data flow, we got better results when the LQWS value was 10. Moreover, we found that the node join and leave operations increase the packet loss. The OLSR protocol has a good performance when the source node is moving. However, the performance is not good when the relay nodes are moving.Peer ReviewedPostprint (published version