On The Recovery Performance of Single- and Multipath OLSR in Wireless Multi-Hop Networks (1206.3838v1)

Abstract: In this paper, we study and improve the recovery properties of single and multipath routing strategies when facing network failure situations. In particular, we focus our study on two MANET routing protocols: OLSR and its multipath extension MP-OLSR. In various wireless multi-hop network environments, especially in multiple chain topologies, we define and seek to evaluate the latency introduced by these protocols to find a new path after a link failure. Theoretical estimations and simulation results show that, under dual chain-topologies, this latency can be too long and incompatible with the needs of loss and delay constrained applications. As the source nodes cannot detect link failures immediately because of the delay incurred by the well-known nature of link state protocols in general, and of OLSR Topology Control (TC) messages in particular, these nodes keep sending packets along broken paths. We thus study the inconsistencies between the actual network topology and the nodes' own representation. After analyzing the consequences of this long latency, we seek to alleviate these problems with the introduction of adapted mechanisms. We propose three new different schemes and accordingly extend the original OLSR and MP-OLSR protocols in order to decrease the expected latency and improve the protocol performance. Simulation results show a steep decrease of the latency when using these new schemes in dual chain-topologies. We also discuss these results in terms of packet loss, end-to-end delay and overhead.

• The paper introduces three novel recovery schemes (RE, FTC, and DR) that significantly shorten link failure response time and reduce packet loss in OLSR protocols.
• Simulations demonstrate that the RE scheme cuts latency to under 1 second in OLSR and that the DR scheme improves multipath performance metrics.
• These innovations enhance network reliability in dual-chain topologies, offering practical solutions for delay-sensitive mobile ad hoc network applications.

Analysis of Recovery Performance in Single and Multipath OLSR

The paper "On The Recovery Performance of Single- and Multipath OLSR in Wireless Multi-Hop Networks" presents a focused paper on the recovery properties of single-path and multipath routing strategies under conditions of network failure, with a particular emphasis on the Optimized Link State Routing (OLSR) protocol and its multipath extension, MP-OLSR. This investigation aims to address significant latency faced in identifying new paths after link failures in Mobile Ad Hoc Networks (MANETs), especially in dual chain-topologies.

The paper identifies a critical issue with existing OLSR and MP-OLSR protocols: the latency in path recovery post link failure, which is problematic for applications sensitive to delay and loss. This latency is attributed to the inherent time delay in link state protocols like OLSR, which rely on periodic Topology Control (TC) messages to update each node's knowledge of network topology. The paper highlights that under dual-chain topologies, such delays render OLSR unsuitable for applications with stringent performance requirements. Within this context, the authors have proposed three novel schemes — a Route Error (RE) notification strategy, a Fast TC (FTC) mechanism, and a Data Re-emission (DR) strategy. These are designed to optimize the recovery performance of both OLSR and MP-OLSR by reducing latency and thus improving overall protocol efficacy.

The numerical findings are of particular interest here. Simulations demonstrate substantial reductions in latency with the new schemes. For example, implementing the RE scheme in OLSR resulted in latencies not exceeding 1 second under various topological scenarios. Similarly, MP-OLSR fortified with the DR mechanism exhibited a consistently lower packet loss ratio and routing load, significantly enhancing performance over the default implementations. The RE scheme provided the most effective latency reduction for OLSR, while the DR scheme notably improved performance metrics for MP-OLSR in general and mobile network topologies. Across the board, the innovations substantially decreased packet loss by about 90% compared to traditional schemes.

These findings underscore important implications for wireless network design, specifically within the context of enabling more robust and efficient backhaul connectivity in Wireless Mesh Networks (WMNs). The practical implications are significant, facilitating improved network reliability and efficiency for bandwidth-intensive applications such as IP telephony or video streaming.

Theoretically, this work contributes to a nuanced understanding of the trade-offs between routing update frequency and control overhead in link state protocols. The introduction of these optimized recovery schemes could herald a shift in how link state protocols are employed in both ad hoc and more static wireless networks.

Looking forward, there are intriguing avenues for further research. One such area involves extending the evaluation of these recovery schemes across different network topologies and conditions, as well as addressing potential Quality of Service (QoS) considerations in packet processing delays, particularly in scenarios where source nodes are aware of flow-specific requirements.

This paper provides a substantive advancement in the ongoing development of fault-tolerant routing protocols, presenting significant evidence of improved efficiencies that suggest future deployments could substantially benefit from these enhancements.