"MANETs are susceptible to various attacks. Out of which Denial of Service (DoS) are most dangerous and very difficult to detect and defend. Jellyfish is a new DoS attack categorized as JF reorder attack, JF periodic dropping attack and JF Delay variance attack. In JF delay variance attack, a JF attacker node intrudes into forwarding group and delays data packets for some amount of time before forwarding. Due to this attack, high end-to-end delay is introduced in the network resulting in low performance (i.e. throughput). In this paper, the effect of JF delay variance attack on MANET using AODV as a routing protocol has been calculated and the performance analysis is done with respect to some network parameters like throughput, end-to-end delay etc."