Proportional bandwidth allocation in DiffServ networks

By analyzing the steady state throughput of TCP flows in differentiated service (DiffServ) networks, we show that current DiffServ networks are biased in favor of those flows that have a smaller target rate, which results in unfair bandwidth allocation. In order to solve this unfairness problem, we propose an adaptive marking scheme, which allocates bandwidth in a manner which is proportional to the target rates of the aggregate TCP flows in the DiffServ network. This scheme adjusts the target rate according to the congestion level of the network, so that the aggregate flow can obtain its fair share of the bandwidth. Since it utilizes edge-to-edge feedback information without measuring or keeping any per-flow state, this scheme is scalable and does not require any additional signaling protocol or any significant changes to the current TCP/IP protocol. It can he implemented in a distributed manner using only two-bit feedback information, which is carried in the TCP acknowledgement. Using extensive simulations, we show that the proposed scheme can provide each aggregate flow with its fair share of the bandwidth, which is proportional to the target rate, under various network conditions.