IJCSNS International Journal of Computer Science and Network Security, VOL.7 No.11, November 2007 85 Manuscript received November 5, 2007 Manuscript revised November 20, 2007 Survey of Service Discovery Protocols and Benefits of Combining Service and Route Discovery Fatma Outay † , Véronique Vèque †† and Ridha Bouallègue ††† , Institute of Fundamental Electronics , Paris Sud University. National Engineering School of Tunis 6’Tel Laboratory, SUP’COM Summary Service discovery is an emerging field in the area of ubiquitous computing. There are various techniques and protocols particularly tailored to specific sets of objectives. This paper analyses the current state of the art and presents taxonomy of service discovery protocols. It demonstrates also the benefits of combining the service discovery with route discovery in MANETs. Key words: MANETs, Service Discovery Protocols, Routing Layer Support. 1. Introduction A service can be any tangible or intangible thing that can be useful for someone. For example when a laborer works for building a house, he is giving his services for which he is paid. Similarly a teacher teaches to his students providing them knowledge that is useful for students. This act of teaching is a service provided by a teacher to his students. In our context of mobile ad hoc networks any facility provided by a device that can be useful for any other device is a service. A service in this context could be a software service like providing an implementation of some algorithm (for example, converting one audio file format to another) on a device so that when some device needs this service, it can contact that device and use it. A service can also be a hardware service like a printer that can be used by a mobile device to print a file. To get benefit from these services a device must be able to locate them in the network and also have the ability to invoke these services [1]. Here comes the role of service discovery protocols. In fixed and wired networks service discovery protocols simplify the interaction among users, devices and services [22]. Service discovery protocols allow devices to automatically discover network services thus making the task of net-work administration and configuration easy. In wireless mobile ad hoc networks devices are free to move. The characteristic limitation of a mobile device is that it has to be small in size and weight. Such devices inherently have few and limited number of resources as compared to fixed devices. So it becomes important to utilize the resources and services available in other devices to accomplish the tasks that cannot be done alone. For example a mobile device without a printing support will require a printer to fulfil the printing task. Thus forming ad hoc network between mobile devices and getting benefit of resources available in a network require knowledge of services available by other devices and how to interact with these services. The service discovery protocols aim at these aspects. More specifically the service discovery protocols not only provide mechanisms for locating a particular service but also mechanisms to advertise a service, invoke a service, select a service if there are more than one services of the same type available and to describe a particular service so as to make its searching easy. There is a lot of research going in the field of service discovery. Basically there are three types of networks as far as the research in service discovery is concerned. First are the wired networks, second are single hop wireless networks and third are the wireless multihop mobile ad hoc networks. The service discovery protocols suggested for one type of network are not suitable for another type of network because each network is based on different assumptions, the most important being the mobility and rate of joining and leaving of devices from the network. In the first type devices do not move at all and there is no join/leave at all or the join and leaves are few and far between. In the second type the network formed is ad hoc with very restricted mobility and having low rate of join/leave. There are one or more nodes that are fixed. But in the third type of network the devices are assumed to have unrestricted mobility and these can join or leave the system at any rate. There may be no fixed node. Due to these assumptions the problem of service discovery is very challenging in the third type of networks.