Implementing and Evaluating the DYMO Routing Protocol

ABSTRACT

In a Mobile Ad hoc Network (MANET), mobile nodes move around arbitrarily, nodes may join and leave at any time, and the resulting topology is constantly changing. Routing in a MANET is challenging because of the dynamic topology and the lack of an existing fixed infrastructure. The Dynamic MANET On-demand (DYMO) protocol builds on previous proposed routing protocols for MANETs. This thesis present a design and implementation of DYMO for Linux and an experimental practical evaluation of DYMO with respect to quantitative performance metrics. The thesis contains a survey of implementation challenges that stem from the lack of system-service support for on-demand MANET routing protocols and a survey of implementation solutions addressing these challenges. The actual implementation consists of a user space routing daemon and a Linux kernel module, based on the netfilter framework. In the practical evaluation, the measured metrics are route discovery latency, TCP and UDP throughput, and end-to-end latency.

Many of the experiments have been conducted in both an emulated and a real setup. Furthermore, the thesis present measurements to determine the limits of TCP based services in MANETs, the so-called ad hoc horizon. The results of the experiments showed performance in the emulated setup to be better than the real setup. In the UDP and TCP experiments, the maximum achieved throughput was 3-4 times better in the emulated setup than in the real setup. Furthermore, the evaluation showed results to be comparable to previous experiments with the related Ad hoc On-demand Distance Vector protocol. The experiments involving the ad hoc horizon indicated that conclusions based on previously obtained simulation results are correct.

INTRODUCTION

The use of wireless technology has become a ubiquitous method to access the Internet or connect to the local network whether in a corporate, educational, or private setting. Practically all laptop computers are currently sold with a built-in wireless adapter. In handheld units like PDAs, wireless adapters have also become standard and are now being introduced in some types of mobile phones. It is much easier and inexpensive to deploy a wireless network compared to a traditional wired network, as the required effort and cost of running cables are negligible. Furthermore, additional devices can be added to the network at no extra cost.

In order for a wireless equipped device to access other computers on the (wireless) local network or connect to the Internet it must associate with a wireless access point. A wireless access point is a device that allows devices equipped with wireless adapters to be linked together in a local area network (LAN) and to connect to a preexisting wired LAN and via a gateway to get access to the Internet. Such networks are called wireless local area networks (WLANs) as the wireless access point is linking wireless devices without wires. Because of the convenience of not having to rely on wires, WLANs have become immensely popular.

When devices equipped with wireless adapters are part of a WLAN and are managed by a wireless access point, their coordination is controlled by a centralized entity. The devices rely on the presence of a fixed infrastructure, i.e., wireless access points to work. Laptop computers must be within the range of a wireless access point to connect to other devices because the laptops must communicate via the access point.