With its new features such as multi-homing, multi-streaming, and enhanced securities, the Stream Control Transmission Protocol (SCTP) has became a promising candidate to join UDP and TCP as a general-purpose transport layer protocol. Multiple streams in an SCTP association provide an aggregation mechanism to accommodate heterogeneous objects, which belong to the same application but may require different types of QoS from the network. However, the current SCTP specification lacks an internal mechanism to support the preferential treatment among its streams, hindered by the fact that all streams share the flow and congestion control at the association level.

In this thesis, 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. Each subflow in the modified SCTP (SF-SCTP) implements its own flow and congestion control in order to avoid false sharing. With those modifications, the SF-SCTP behaves similarly as an aggregation of SCTP associations, which is too aggressive and can steal bandwidth from the competing network traffics. To make the SF-SCTP more TCP-friendly and to reduce its aggressiveness, we further integrate the mechanism called Fractional Congestion Control (FCC) into the design of SF-SCTP.

Analytical models for the original SCTP, SF-SCTP without FCC and SF-SCTP with FCC are derived based on existing TCP throughput models. Our models improve the existing TCP models and are suitable for both Drop-Tail and RED queues, and for different packet sizes. In addition, our models can be used to predict the performance of a network designed to support differentiated services.

Performance evaluation and comparison of original SCTP, SF-SCTP without FCC and SF-SCTP with FCC are studied through a set of extensive simulation experiments. The results show that the proposed SF-SCTP design is able to support QoS among the SCTP streams and that false sharing is avoided. The results indicate SF-SCTP's significant benefits in improving the utilization of a bottleneck network. The results also reveal that, with FCC integrated, SF-SCTP is capable of taking advantages of differentiated services offered by a network, while maintaining fairness to other TCP-friendly traffics.