Two bits are enough

We design a congestion control protocol that uses the existing IP ECN bits to achieve efficient and fair bandwidth allocations on high Bandwidth-Delay Product (BDP) paths while maintaining low persistent queue length and negligible packet loss rate. Our protocol uses load factor as a signal of congestion and makes use of a packet marking scheme to obtain high resolution congestion estimates. Our scheme reduces the Average Flow Completion Time (AFCT) by up to 70% when compared with VCP and by up to 45% when compared with TCP SACK+RED/ECN.