Systems and methods of mitigating DOS attacks on a victim node in a computer based communication system are presented. According to the methods a node such as a router upstream from the victim analyzes traffic flow directed to the victim node and if a pattern indicating a possible attack is detected a notification to the effect is sent to the victim node. The victim can either ignore the notification or chose to suggest or request attack mitigation measures be implemented by the upstream router. Alternatively the upstream router can implement attack mitigation measures without waiting for input from the victim node.