Max-min fair rate allocation for VCP in multi-bottleneck networks

Variable-structure congestion Control Protocol (VCP) leverages the existing two Explicit Congestion Notification (ECN) bits for network congestion feedback and achieves comparable performance to eXplicit congestion Control Protocol (XCP). VCP utilises the encoded load factor-based feedback scheme to deliver congestion signals. In multi-bottleneck networks, all bottleneck links on the transmission path would contribute to the aggregate congestion signal, and VCP fails to achieve max-min fairness. To address this problem, a new metric called overload period is introduced to measure the congestion level of links, and the overload period-based feedback scheme is proposed to make sure that each VCP flow's rate is controlled only by the link with minimum overload period encountered on the transmission path. It is proved that the link with minimum overload period is the flow's bottleneck, and the max-min fair rate allocation is achieved in multi-bottleneck networks. The overload period-based feedback scheme is validated using NS2 simulations.