Abstract: MANET nodes rely on network cooperation schemes to properly work. Node cooperation is important since there is no fixed infrastructure and central authority in MANET. There is the possibility of existence of nodes refuse to cooperate by not forwarding data in order to save its own energy and resources. Presence of selfish node degrades network performance by increasing packet dropping. Collaborative watchdog introduces an efficient approach to reduce the detection time of selfish nodes based on contact dissemination. If one node has previously detected a selfish node using its watchdog it can spread this information to other nodes when a contact occurs. This method does not consider presence of malicious node and detection function to be implemented in every pair of nodes. In this paper, we propose a new framework which uses a trust based scheme and watchdog to detect selfish node.Also alert model is implemented in which node which are not ready to cooperate can send warning messages to adjacent nodes. Trust relationship must be set up between every pair of nodes. Packet forwarding ratio and energy is used to maintain trust between nodes. Watchdog functions are implemented in trusted node only. It reduces the overhead of implementing watchdog in every node.

Keywords: selfish node, reputation, trust, mobile ad hoc networks (MANETs).