Chirping for Congestion Control - Implementation Feasibility∗

We present lessons from implementing a bandwidth probing scheme termed chirping as part of congestion control in the Linux kernel. Chirping was first introduced for bandwidth estimation in the pathChirp tool. A chirp is a group of several packets that are sent with decreasing inter-packet gaps in order to continuously probe for spare bandwidth. Current congestion control schemes are either slow to find new bandwidth or they overshoot due to lack of fast feedback information. The attraction of using chirping as a building block for congestion control is to be able to non-intrusively probe for available capacity in a very short time. But implementing chirping is challenging because it requires an exact timing of every packet which is very different to the traditional approach in the network stack. As there are changes needed at the receiver as well, we also discuss a potential approach for deployment. Success in detecting fast feedback information using chirping opens the possibility of future work on new congestion control designs that should be more responsive with less overshoot.