There were clear differences between the DDoS attack on 7th July 2009 and the rest of them prior to the attack. Despite It had emitted relatively small sized packets per infected PC, the attack was very successful making use of HTTP Flooding attack by aggregating small sized packets from the well sized zombie network. As the objective of the attack is not causing permanent damage to the target system but temporal service disruption, one should ensure the availability of the target server by deploying effective defense strategy. In this paper, a novel HTTP based DDoS defense mechanism is introduced with capacity based defense-in-depth strategy.