TCP Congestion Control with a Misbehaving Receiver

This paper discusses how a TCP receiver can misbehave by defeating congestion control measures through various attacks. The three attacks described are ACK Division, DupACK spoofing, and Optimistic ACKing. An ACK Division attack divides an acknowledgment for a data segment into multiple separate acknowledgments. DupACK spoofing involves sending back multiple acknowledgments for the last data segment received, and Optimistic ACKing is preemptive sending of acknowledgments for data that has not yet been received.

The first two cause the sender to send packets in a quick burst by quickly expanding the congestion window, while the third causes the sender to send data sooner than it originally would have. All three attacks were generally successful against the TCP implementations of a variety of OSes. The authors use a simple HTTP request in their test and provide graphs that clearly show that their exploits worked. The attacks were able to be implemented with a disturbingly small amount of code.