# Analysing the Performance of a Trust-Based AODV in the Presence of a Flooding Attack
## 2 Related Work
Each node in a MANET monitors the behaviour of its neighbouring nodes by analysing the RREP packet received. If an intermediate node detects a malicious node after receiving an RREP packet, it labels the RREP packet _do not consider_ and marks the node as a _malicious node_ in the routing table. The intermediate node will reverse the path, sending the RREP packet back towards the source node, which will update the routing tables of all nodes with the malicious node entry. The new route towards the destination node is selected by unmarked RREP packets. [PERSON] et al. [13] proposed an algorithm to detect black-hole and grey-hole attacks by adding extended data routing information to the routing table in the AODV protocol. The routing table exists in every node in the network and fields are added to detect malicious nodes and save a history of their previous malicious activities. Creating a historical record for each node's malicious activities is a way of addressing grey behaviour. This mechanism is built on the AODV protocol. [PERSON] et al. [14] proposed an idea called \"watchdog\", which is a direct trust management mechanism and a path rater. Each node in the network listens to the transmissions of the next node along the route to detect malicious behaviours. The path rater holds the trust values of the nodes, which range from 0 to 0.8, with neutral taking the value of 0.5. These values given to the nodes are updated continuously by 0.1 each 200 ms. The source node should be able to detect selfish nodes and avoid sending packets to them. This scheme has shown better performance in the presence of selfish attacks. However, it also increases the memory overhead as the watchdog mechanism needs to maintain the information collected from the packets. [PERSON] and [PERSON] [15] proposed an amended routing protocol called Cooperation Of Nodes - Fairness In Dynamic Ad hoc Networks (CONFIDANT). This improved protocol contains a trust management and reputation system. While monitoring the behaviour of the neighbouring node, the trust manager evaluates the node's activities and sends alarms to neighbouring nodes telling them about a malicious node. The malicious node is then isolated by all nodes that receive the alarm. This mechanism combines direct monitoring and a reputation system. The mechanism has shown better performance in the presence of black-hole attacks. [PERSON] and [PERSON] [16] suggested a collaborative reputation scheme based on collaborative monitoring. This schema has a more complicated reputation system in which it is not only one node monitoring the behaviour of the next node, but many nodes monitoring the behaviour of the same nodes. The decision is made using the data collected by all nodes involved in the network. The decision here should be more accurate than using other methods because it is not made by an individual node. Each node has a reputation table and a watchdog mechanism. Each node monitors the behaviour of its neighbours, assigns trust values to them and saves those values in its trust table. The nodes share their trust values with each other. This mechanism has shown better performance in the presence of selfish attacks. [PERSON] et al. [17] proposed a secure MANET routing protocol based upon a direct trust mechanism establishing the trust level of the nodes along the route. This protocol stores trust values in the RREQ packet. When the source node wishes to initialise a route to the destination, it sends the RREQ packet to its neighbouring node. The intermediate node updates the trust values in the RREQ packet and forwards it to the next node. When the RREQ packet reaches the destination node, the destination node replies to the source by sending an RREP packet containing the level of trust of the route. Then the source can choose the route with the highest trust level rather than choosing the shortest route. [PERSON] et al. [18] proposed a reputation-based trust model called secure MANET routing with trust intrigue.