<span lang="en">This paper proposes a service descovery protocol for discovering and advertising services in a proactive ad hoc network. The protocol we have defined is piggybacked into the OLSR (Optimized Link State Routing) routing protocol. We have defined a new message type into OLSR, called Service Discovery Message (SDM), for both advertisement and discovery of services. The advertisement frequency and advertisement lifetime are user-controlled parameters, so that they can be modified depending on the user requirements. Each node mantains a service cache to store information about its own services, and the services each device discovers in the network. We also present simulation results of our protocol and show that the service discovery protocol defined here, achieves much efficiency in discovering services, while it introduces practically no packet overhead compared to the basis OLSR protocol.</span>