Routing overlay for a mobile Ad Hoc network: Master's thesis

Overlay networks are built on top of an existing network, using its services for building overlay network topology. The routing in overlay networks functions on the overlay level, using various different technologies. The choice of the routing architecture depends on the nature of the overlay network. The purpose of an overlay network is to provide functionality that the underlying network cannot provide. This thesis is a study of overlay routing for a mobile ad hoc network, in which the topology can change arbitrarily and even the whole network can be mobile. This places requirements on the routing protocol used, and requires mobility support from the nodes. However, a lot of the mobile devices with short-range connectivity do not have support for mobility, and do not allow the user to modify their network stack. In this kind of device the routing layer has to be implemented as an overlay, and this thesis presents a design for it. The design builds pipe connections between the nodes of the overlay network and routes the packets through these pipes until they reach their destination. The design enables the overlay nodes to function with the network’s non-overlay nodes by presenting bridging software. The support for mobility and the ad hoc routing protocol are hidden from the user, and a simple API is provided for sending and receiving data. The network is dynamic; no static configuration is needed. In the experimental part of this thesis, a prototype of the overlay routing solution was developed on a Symbian device. The device was functioning in a network built on the Linux platform. This network was not an overlay network, so the Symbian device had to be integrated with it by the bridging software. The prototype was tested by communicating with the Symbian device through the Linux platform. The resulting overlay network adds overhead to the communication, but it is tolerable. The presented design can work over multiple platforms and it exploits the services of the underlying network. The user of the network is not required to implement the whole network stack and the communication hardware, only the overlay software layer. In conclusion, the overlay network created in this thesis is a reasonable solution.