Service discovery mechanism over OLSR for mobile ad-hoc networks

This paper considers the subject of provisioning services in ad-hoc networks. Service discovery in these networks is challenging due to the lack of central infrastructure, limited resources and high mobility. We propose integrating this mechanism on the proactive OLSR (Optimized Link State Routing) protocol. A new message type, called Service Discovery Message (SDM), is added. This message will announce (servers) and request (clients) for services. Available local services will only be advertised once, with a specific lifetime, in order to avoid increasing the network overhead. These services will be stored in a local service cache that is maintained on each node. When a node wants to make use of a service, it will look on the cache. If it is not yet stored, it will send a query message. Simulation results are presented to demonstrate that the introduced packet overhead is insignificant compared with the standard OLSR protocol. These mechanisms must be efficient: every node should know the maximum number of services as possible. In networks with few nodes, the percentage of discovered services is around 90%. On the other hand, in bigger networks, was higher than the 80%. We believe that due to the obtained results, the following step consists on proving the protocol here presented in real scenarios using prototypes.