On explicit congestion notification for stream control transmission protocol in lossy networks

As a congestion avoidance mechanism, Explicit Congestion Notification (ECN) is designed to inform a data source to react to potential congestion early. Currently, the new transport protocol, Stream Control Transmission Protocol (SCTP), is not ECN-capable. An ECN-capable SCTP is proposed in this paper, which is bandwidth-efficient and robust to non-congestion losses. An SCTP source needs to adjust its congestion window when receiving ECN messages. We find the optimal value of the congestion window for an SCTP source in response to ECN messages, and develop a simple and practical method to achieve this optimal congestion window. Both simulation results and analysis are provided to support the effectiveness of the proposed ECN mechanism for SCTP. The simplified method in achieving the optimal congestion window is attractive because the total goodput performance of SCTP associations or the bottleneck link utilization is not sensitive to the window reduction policies when the network load is heavy. Using complicated methods to fine-tune SCTP or TCP's congestion window in response to congestion indications may not be worth the increase in complexity of the protocol.