To mitigate black hole attack in AODV

MANETs is a collection of mobile nodes. There infrastructure is neither fixed nor has any control station. So it is affected by various types of malicious attack. AODV is a standard MANETs protocol so every malicious node tries to attack on this routing protocol. A black hole attack is a type of malicious attack in which black hole node replies to route request packet with the highest destination sequence number and lowest hop count to the source node and source node send data packets to this node but it does not have route to the destination nodes so it simply drops the data packets or absorb it. To prevent black hole attacks in AODV it requires secure route discovery. In secure route discovery the destination node and the source node verifies the sequence numbers in the Route Reply and Route Request messages respectively. This paper adds extra function at source node as well as destination node so whenever a RREP or RREQ message comes to the respective node it checks the sequence number of the packets and compares it with the threshold value. The threshold value is defined for three environments small, medium and large and compare it with respective environment threshold value.