**4. Response component : Geographic, energy and trust aware routing (GETAR) protocol**

In this section, an enhanced routing protocol that aims to provide a secure packet delivery service guarantee by incorporating the trust awareness concept into the routing decision is presented. Our proposed protocol is called Geographic, Energy and Trust Aware Routing (GETAR) which is an enhanced version of the Geographic and Energy Aware Routing (GEAR) protocol [9]. GEAR is basically a geographic routing protocol in which the next hop is selected based on two metrics: the distance between the next hop and the destination and the remaining energy level the next hop owns. The new contribution in GETAR is to add a third metric in the next-hop selection process, i.e. the risk value of a node that is computed by the rating component, CRATER in our case.

After a node monitors its neighborhood using EMPIRE and rate them based on CRATER, the node should make the proper response that leads to a proper routing decision. Assume that node A computed a risk value for a malicious neighboring node, B. Then, node A may or may not respond to B's behavior. Since our system treats the secure routing purpose, A should respond in a proper manner. Among different possible reactions provided in many reputation systems [3, 5, 72], we can identify three main response approaches:


In this work, the defensive approach where malicious nodes are simply avoided without any further actions against them is adopted.
