Throughput models for SCTP with parallel subflows

Multi-streaming provides SCTP with an aggregation mechanism to accommodate heterogeneous objects, which belong to the same application but may require different type of QoS from the network. However, in the current SCTP specification, supporting QoS inside an SCTP association is not a concern; it is also hindered by the fact that all streams share the flow and congestion control at the association level. We introduce the concept of subflow and propose to modify the current SCTP such that the streams are grouped into several subflows according to their required QoS. To prevent false sharing, each subflow in the modified SCTP (SF-SCTP) implements its own flow and congestion control. Our design also integrates fractional congestion control to improve the fairness of the modified SCTP towards other network traffic. Analytic models are presented to compare the throughput of the original SCTP and SF-SCTP using different flow and congestion control mechanisms. Simulations with ns-2 are used to estimate the throughput in a simplified Diff-Serv network. The analytic models are confirmed to accurately reflect the SCTP behavior. The simulation shows that our proposed solution is able to support QoS among the SCTP streams, and that it achieves a better throughput. The results also indicate that SF-SCTP is more fair to the original SCTP after fractional congestion control is introduced.