The Cooperative Intrusion Traceback and Response Architecture (CITRA) [1] and the Intruder Detection and Isolation Protocol (IDIP) [2] provide an infrastructure that enables intrusion detection systems, firewalls, routers, and other components to cooperatively trace and block network intrusions as close to their sources as possible. We present the results of recent testbed experiments using CITRA and IDIPto defend streaming multimedia sessions against the Stacheldraht DDoS toolkit. Experimental data suggests that these technologies represent a promising approach for autonomic DDoS defense.