Relentless Congestion Control

Relentless congestion control is a simple modification that can be applied to almost any AIMD style congestion control: instead of applying a multiplicative reduction to cwnd after a loss, cwnd is reduced by the number of lost segments. It can be modeled as a strict implementation of van Jacobson's Packet Conservation Principle. During recovery, new segments are injected into the network in exact accordance with the segments that are reported to have been delivered to the receiver by the returning ACKs.

This algorithm offers a valuable new congestion control property: the TCP portion of the control loop has exactly unity gain, which should make it easier to implement simple controllers in network devices to accurately control queue sizes across a huge range of scales.

Relentless Congestion Control conforms to neither the details nor the philosophy of current congestion control standards. These standards are based on the idea that the Internet can attain sufficient fairness by having relatively simple network devices send uniform congestion signals to all flows, and mandating that all protocols have equivalent responses to these congestion signals.

To function appropriately in a shared environment, Relentless Congestion Control requires that the network allocates capacity through some technique such as Fair Queuing, Approximate Fair Dropping, etc. The salient features of these algorithms are that they segregate the traffic into distinct flows, and send different congestion signals to each flow. This alternative congestion control paradigm is described in a separate document, also under consideration by the ICCRG.

This page will be used to post general information about relentless congestion control, including pointers to implementations, papers and user experiences.