Abstract: IP traceback scheme has become one of the efficient coutermeasures to prevent the Denial Of Service（DOS） attack.Particularly，Probabilistic Packet Marking（PPM） first developed by Savage et al is promising and has many variants.But because of its overwritten marking and fixed marking probability，there exists the weakest link problem，which results in poor convergence of path reconstruction in PPM.A new scheme of un-overwriting PPM for IP traceback is presented.The convergent amount of marked packets requires path reconstruction and the computation overhead be both efficiently improved，and the efficiency of path reconstruction is increased.

摘要： IP追踪已成为防御拒绝服务攻击（DOS）的有效方案之一。其中，以Savage等人提出的概率包标记（PPM）已受到广泛重视。然而，概率包标记因为重复标记和固定概率而存在最弱链问题，从而导致重构路径的弱收敛性。提出一种新型的非重复性包标记的IP追踪方案，有效地减少了重构路径时的收敛时间以及计算开销，提高了路径重构的效率。