Latency Reduction for Soft Real-Time Traffic using SCTP Multihoming

Sammanfattning: More and more so-called soft real-time traffic is being sent over IP-based networks. The bursty, data-limited traffic pattern as well as the latency requirements from this traffic present challenges to the traditional communication techniques, designed for bulk traffic without considering latency.To meet the requirements from soft real-time traffic, in particular from telephony signaling, the Stream Control Transmission Protocol (SCTP) was designed. Its support for connectivity to multiple networks, i.e., multihoming, provides robustness and opens up for concurrent multipath transfer (CMT) over multiple paths. Since SCTP is a general transport protocol, it also enables for handover of media sessions between heterogeneous networks. Migrating an ongoing session to a new network, as well as CMT with minimal latency, requires tuning of several protocol parameters and mechanisms.This thesis addresses latency reduction for soft real-time traffic using SCTP multihoming from three perspectives. The first focus is on latency for signaling traffic in case of path failure, where a path switch, a failover, occurs. We regard quick failure detection as well as rapid startup on the failover target path. The results indicate that by careful parameter tuning, the failover time may be significantly reduced. The second focus in the thesis is on latency for signaling traffic using CMT. To this end, we address sender-side scheduling. We evaluate some existing schedulers, and design a dynamic stream-aware scheduler. The results indicate that the dynamic stream-aware scheduler may provide significantly improved latency in unbalanced networks. Finally, we target multihomed SCTP to provide for handover of a media session between heterogeneous wireless networks in a mobile scenario. We implement a handover scheme and our investigation shows that SCTP could provide for seamless handover of a media session at walking speed.