Performance Analysis and Improvement of PR-SCTP in an Event Logging Context
Mohammad Rajiullah · Diva portal (Dalarna University Library) · 2012
Due to certain shortcomings in TCP and UDP, the Stream Control Transmission Protocol (SCTP) was defined for transporting telephony signaling traffic. The partially reliable extension of SCTP, PR-SCTP, has been considered as a candidate for prioritizing content sensitive traffic and trading reliability against timeliness for applications with soft real time requirements. In this thesis, we investigate the applicability of PR-SCTP for event logging applications. Event logs are inherently prioritized. This makes PR-SCTP a promising candidate for transporting event logs. However, the performance gain of PR-SCTP can be very limited when application message sizes are small and messages have mixed reliability requirements. Several factors influence PR-SCTP’s performance. One key factor is the inefficiency in the forward_tsn mechanism of PR-SCTP. We examine the inefficiency in detail and propose several solutions. Moreover, we implement and evaluate one solution that utilizes the Non-Renegable Selective Acknowledgements (NR-SACKs) mechanism currently being standardized in the IETF, which is available in the FreeBSD operating system. Our results show a significant performance gain for PR-SCTP with NR-SACKs. In some scenarios, the average message transfer delay is reduced by more than 75%. Moreover, we evaluate NR-SACK based PR-SCTP using real traces from an event logging application called syslog. It significantly improves the syslog application performance as compared to SCTP, TCP and UDP.