# MPH-M, AODV-M and DSR-M Performance Evaluation under Jamming Attacks
## 4 Proposed Mitigation Mechanism for Jamming Attacks
### Routes Reconfiguration  
To isolate the nodes affected by the jamming from the network, the routes reconfiguration should be done. This reconfiguration step depends on the routing protocol, either ADOV, DSR or MPH. Next, we will explain how these protocols work. AODV is a reactive protocol that sends hop by hop packets. The routes have an expiration time and this protocol represents a decrease in the processing of nodes, decreases the expense in memory and reduces control traffic. In order to keep only the most efficient routing information, AODV has the concept of sequence number for packets. This number is an integer value that each node increments before generating a control message to copy it to the packet before sending it. The lifetime of the route is the time the route expires or must be deleted. This prevents lost packets to be traveling on the network and using links whose status has not been known for a long time. AODV has the advantage of repairing small faults in the network before notifying to the others nodes, in order to avoid using bandwidth [28]. DSR is based on source routing. Nodes maintain caches, whose entries include the destination and the list of nodes to reach it. This protocol consists of two main mechanisms: path discovery and route maintenance. The source node is responsible for discovering the route from each source node to the destination node. This can generate a bit of latency if the packets have too long headers for routes. Once the route is established, then maintenance mechanism starts. The latter steps consist in to keep monitoring the error of the received packets in each node of the route [28]. MPH is a proactive, hierarchical multi-parent protocol that establishes links based on node hierarchy, starting from the highest hierarchy node, which is the coordinator node. This type of protocol has fewer links per node, then the other routing protocols because it only allows parent-child links, but does not allow links between nodes with the same hierarchy level. Path reconfiguration is performed by HELLO packets that are sent periodically in order to check if the neighbors of a node still exist. If no response is received from these nodes, they are removed from the neighbor table and are no longer used as valid routes. This is where network topology changes because hierarchy levels of the nodes change. When a notification of jamming is received by node \(i\) from node \(j\), node \(i\) will adjust its neighbor table removing node \(j\), thus \(j\) is not considered as a neighbor of \(i\) and a reconfiguration of routes in the network will be carried out by the routing protocol. Figure 2 shows the coverage radii of two nodes in the network. We take as an example the radius of the jammer node and the radius of an arbitrary node in the network. We can observe that when there is a positive jamming detection, the node sends a control packet that causes its neighbors to remove it from their neighbor tables. In this way, according to the coverage radius, as a hypothesis, we can argue that nodes surrounding the jammer node will be removed from the network, causing reconfiguration of routes. This is because these nodes, according to the graph, can lose packets coming from other nodes that are not directly affected by the jammer node. The effect of removing a node as a neighbor is that it reduces the probability of having a high packet loss. Reconfiguration of routes in the WSN is carried out differently for each of the protocols considered in this paper. When routes change, due to the presence of a malicious node, AODV runs a mechanism of error messages and also puts in each created route an expiration time (Time To Live). If there is a node that does not respond during that time, the route is taken as invalid and becomes obsolete. The DSR protocol only handles error packets for route maintenance.