BFC+: Analysis and Improvement of the Congestion Control Algorithm BFC

BFC is a per-flow per-hop congestion control method published in NSDI in 2022. BFC utilizes router support for multiple queues to perform per-flow per-hop level traffic scheduling within the network to maximize link utilization without requiring endpoint participation. A necessary condition for BFC to perform optimally is that routers must have sufficient buffer space and be able to truly isolate multiple flows within the same router. However, our experiments found that BFC's queue allocation algorithm cannot always effectively isolate multiple flows. BFC determines whether a queue is available by checking if the queue is empty, but in actual networks, it is common for queues to be empty during the absence of congestion or in the early stages of congestion. This can mistakenly allocate multiple flows to the same queue, causing BFC's scheduling ability to not perform optimally. This paper solves this problem and proposes an improved method called BFC+. Our experiments show that compared to BFC, BFC+'s queue allocation is more reasonable and has better performance.