Implementation of a Multihoming Mobile Router for Multimedia Communication on Public Transport


There is an increasing interest in deploying high speed LANs on public transport vehicles to allow traveler to connect their devices to the Internet. An on-board network typically consists of a high speed mobile LAN and a mobile router that provides connectivity to the Internet through wireless links. The mobile users simply connect their devices to the on-board network to enjoy the Internet service.

To improve the aggregate bandwidth and the overall service availability, the idea of using multiple access links simultaneously (so-called multihoming) has been commonly employed by large enterprises and data centers as a mechanism to ensure good performance and network reliability from their ISPs [1][2]. Multihoming issues are also frequently discussed in IETF’s NEMO and Mobile IP Working Group [3]. In this project, we plan to develop a prototype implementation of an Intelligent Multihoming router for improving the performance and reliability of on-board networks.

Related work

Current mobile devices are often equipped with several network interfaces [4], which may be of different access technologies. Different requirements of different applications can result in a different preference of the interface that should be used. Network connections should be placed on the best possible interface based on these requirements. During communication, changes in the availability or characteristics of an access network an interface connecting to may result in change of preference of interfaces for new connections and previously-established connections.

Several Internet drafts [5] [6] [7] [8] introduce the requirements and definitions for IPv4 and IPv6 multihoming. They present a few implementation proposals for interface selection in the host multihoming that would allow explicit policy definition. They also identify the interface selection problem and mention that the selection should be based on some policies. But they do not look into the details of implementing policy-based interface selection system.

Ylianttila et. al [9] present a handoff case study between GPRS and WLAN based on mobile IP. They have discussed about procedures, algorithms and metrics involved in handoff in heterogeneous wireless networks. A procedure is given for inter-technology roaming between WLAN and GPRS. They envision that WLANs should be integrated into wide area wireless data networks since the wideband wireless services might not have a comprehensive coverage. In their implementation, the handoff information is gathered at link layer (e.g. signal strength) and used by a daemon program at the application level for decision making. Handoffs are made on account of implicit rules utilizing fuzzy logic.

Jukka Ylitalo et al [4] present an interface selection architecture, which allows a user to dynamically create and modify interfaces selection policies and thus control how the network interfaces are used in a multihoming environment. The architecture makes it possible to define policies for different connections on account of user preferences. Each connection is bound to a profile that contains local routing rules. Therefore, it is possible to make a vertical handoff to a single connection or to a group of connections without affecting any other connections that are using the same interface.

Pablo Rodrigueze et al present in [10] a Mobile Access Router that utilizes multiple wireless access links to aggregate bandwidth and provide local users with a smoother, more reliable access network than can typically be provided by a single cellular link. A policy-based interface selection system is also implemented. Based on a particular MAR scheduling policy, MAR selects a given interface for each packet or request based on NAT technique. A case study for exploiting the network diversity in wireless access is provided. Experiments with production networks show that there is a substantial overlap in terms of coverage being offered by many of these operators and also across networks. However, their implementation doesn't take any user defined policy into account.




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