One more bit is enough

摘要: Achieving efficient and fair bandwidth allocation while minimizing packet loss bottleneck queue in high bandwidth-delay product networks has long been a daunting challenge. Existing end-to-end congestion control (e.g., TCP) traditional notification schemes TCP+AQM/ECN) have significant limitations achieving this goal. While the XCP protocol addresses challenge, it requires multiple bits to encode congestion-related information exchanged between routers end-hosts. Unfortunately, there is no space IP header for these bits, solving problem involves non-trivial time-consuming standardization process. In paper, we design implement simple, low-complexity protocol, called variable-structure (VCP), that leverages only existing two ECN network feedback, yet achieves comparable performance XCP, i.e., utilization, negligible rate, low persistent length, reasonable fairness. On downside, VCP converges significantly slower than XCP. We evaluate of using extensive ns2 simulations over wide range scenarios find outperforms many recently-proposed TCP variants, such as HSTCP, FAST, CUBIC, etc. To gain insight into behavior VCP, analyze simplified fluid model prove its global stability case single shared by synchronous flows with identical round-trip times.