Competitive and Considerate Congestion Control for Bulk Data Transfers

We propose a novel transport control protocol, Competitive and Considerate Congestion Control (4CP). This yields a fixed per-flow bandwidth to other connections (e.g. TCP) if the network can support this and uses the residual bandwidth for 4CP. The main contribution is a novel window based congestion controller that combines congestion phase detection and congestion window control to achieve the stated bandwidth sharing objective. 4CP may be viewed as a non strict low priority emulator. Consequently, 4CP does not suffer from bandwidth starvation when competing with a single TCP connection. Furthermore, when congestion is low, 4CP can utilise residual bandwidth. When congestion is high, 4CP will back-off. The properties of 4CP described above, suggest its applicability for bulk data transfer applications that must be considerate of competing traffic whilst still making transfer progress themselves. We present analytical results, simulation findings and Internet experiments that demonstrate validity of 4CP in addition to guidance on parameter setting.