I. Introduction
Distributed Denial of Service attack impose an alarming threat to the operation of internet services which floods the victim with a tremendous amount of traffic and exhaust the victim's resources thereby making its services unavailable to the user. It is difficult to defend against DDoS attack as it is originated from a large number of compromised attack agents [1] [2]. No effective solution has been devised for this serious threat because the attackers keep changing their attacking patterns and attack source IP address constantly. In this arena of attacks, IP traceback has become one of the major and vital solutions for tracing the attack origin. From the network forensics view, to identify the actual source and the network path used by the packet, IP traceback mechanism is employed [3] [4]