MeshScan: a Fast and Efficient Handoff Scheme for IEEE 802.11 Wireless Mesh Networks

As a next generation network solution, Wireless Mesh Networks (WMN) provides fast Internet access to a large area, which is from university campus to city scale. In order to provide an uninterrupted Internet experience to a mobile client, a process called handoff is required to maintain the network connection from one Mesh Node (MN) to another MN. Ideally, handoff should be completely transparent to mobile users. A critical application like VoIP will require a handoff capability that transfers a call from one mesh node (MN) to another in less than 50 msec. However the current IEEE 802.11 standards do not address the handoff well. Studies have revealed that standard handoff on IEEE 802.11 WLANs incurs a latency of the order of hundreds of milliseconds to several seconds. Moreover, the discovery step in the handoff process accounts for more than 99% of this latency. The study addresses the latency in the discovery step by introducing an efficient and powerful client-side scan technique called MeshScan which replaces the discovery step with a unicast scan that transmits Authentication Request frames to potential MNs. A prototype of MeshScan has been developed based on the MadWifi WLAN driver on Linux operating systems. The feasibility of MeshScan to support fast handoff in WMNs has been demonstrated through extensive computer simulations and experiments under same given conditions. The results from the simulations and experiments show that the latency associated with handoff can be reduced from seconds to a few milliseconds by using the MeshScan technique. Furthermore, it is shown that MeshScan can continue to function effectively even under heavy traffic loads

Controlo de mobilidade com segurança em redes estruturadas 802.11

Mestrado em Engenharia Electrónica e TelecomunicaçõesEsta dissertação aborda o problema da gestão da mobilidade com segurança em redes 802.11. Assim, começa por apresentar um estudo detalhado do protocolo 802.11, do handoff de dispositivos móveis entre pontos de acesso e de soluções apresentadas por diversos autores com o objectivo de reduzir o tempo dispendido neste processo, com e sem segurança associada. Seguidamente, são apresentadas métricas e atributos de rede que podem ser considerados no estabelecimento de políticas de mobilidade que gerem as transições de AP que cada dispositivo móvel efectua. Uma vez feito este estudo inicial, é apresentada uma solução que potencía handoffs rápidos e seguros em redes estruturadas 802.11 e que minimiza o tempo da sua preparação. Este novo protocolo representa uma evolução do trabalho desenvolvido por Rodolphe Marques no trabalho intitulado “Segurança e Mobilidade em Redes Estruturadas 802.11” referenciado em [1]; a sua novidade consiste em usar tramas 802.11 de reconhecimento da rede (Probe Request/Response) para difundir associações de segurança com os pontos de acesso ao alcance de cada dispositivo móvel. A nova abordagem implica mudanças reduzidas na arquitectura de rede considerada em [1] e permite que, no âmbito das operações de reconhecimento de pontos de acesso, que são comuns e necessárias, um equipamento móvel instale paralelamente associações de segurança nos APs que poderá vir a usar num futuro próximo, ou seja, todos os que estão ao seu alcance. ABSTRACT: This thesis handles the problem of mobility management with security in 802.11 networks. Therefore it begins by presenting a detailed study of the 802.11 protocol, the handoff process of roaming mobile nodes between access points and solutions presented by many authors with the common goal of reducing the time spent in this process, with and without associated security. After this we present metrics and attributes of the network that may be considered on the establishment of mobility policies that handle the AP transitions made by every mobile node. Once finished this initial study we present a solution that enhances fast and secure handoffs in structured 802.11 networks and minimizes the time spent in its setting. This new protocol represents an evolution on the work developed by the author Rodolphe Marques in his work named “Security and Mobility in 802.11 Structured Networks” referred in [1]; its new feature consists in using 802.11 network scanning frames (Probe Request/Response) to distribute security associations to all access points in range of each mobile node. This new approach implies some changes on the architecture proposed in [1] and allows a mobile node to install security associations simultaneously while browsing the neighborhood for access points that may be used in a near future

Fast and seamless mobility management in IPV6-based next-generation wireless networks

Introduction -- Access router tunnelling protocol (ARTP) -- Proposed integrated architecture for next generation wireless networks -- Proposed seamless handoff schemes in next generation wireless networks -- Proposed fast mac layer handoff scheme for MIPV6/WLANs