Survey of Service Discovery Protocols in Mobile Ad Hoc Networks1

Mobile devices are inherently scarce in resources, necessitating the need to cooperate among them for performing tasks that cannot be done alone. This cooperation is in the form of services that are offered by other devices in the network. To get benefit from the services offered by other devices, they have to be discovered. Service Discovery Protocols (SDPs) are used for this purpose. This is an important area of research in mobile computing and ubiquitous computing. In this paper twelve SDPs for multihop mobile ad hoc networks are analyzed with respect to their service discovery architectures, management of service information, search methods, service selection, methods for supporting mobility and service description techniques, Among these the most important aspect is the service discovery architecture as this affects other aspects of the service discovery. In this paper the service discovery architectures are categorized in four groups namely directory-based with overlay support architecture, directory-based without overlay support architecture, directory-less with overlay support architecture and directory-less without overlay support architecture. The management of service information and search methods mainly depend on the type of service discovery architecture. It is found that mobility support and service selection methods are independent of the SDP architecture. Also the description of services is found to be independent of the SDP architectures. Mostly the services are described using XML or the extensions of XML. At the end of the paper open issues and areas of further research are discussed.