TCP Performance Issues Research Articles

TCP Stalls at the Server Side: Measurement and Mitigation

TCP is an important factor affecting user-perceived performance of Internet applications. Diagnosing the causes behind TCP performance issues in the wild is essential for better understanding the current shortcomings in TCP. This paper presents a TCP flow performance analysis framework that classifies causes of TCP stalls. The framework forms the basis of a tool that we use to analyze packet-level traces of three services (cloud storage, software download, and web search) deployed by a popular service provider. We find that as many as 20% of the flows are stalled for half of their lifetime. Network-related causes, especially timeout retransmissions, dominate the stalls. A breakdown of the causes for timeout retransmission stalls reveals that double retransmission and tail retransmission are among the top contributors. The importance of these causes depends however on the specific service. Based on these observations, we propose smart-retransmission time out (S-RTO), a mechanism that mitigates timeout retransmission stalls through careful and gentle aggression for retransmission. S-RTO is evaluated in a controlled network and also in a production network. The results consistently show that it is effective at improving TCP performance, especially for short flows.

TCP Performance Issues in Satellite and WiFi Hybrid Networks for High-Speed Trains

TCP Performance Issues in Satellite and WiFi Hybrid Networks for High-Speed Trains

TCP Performance in Flow-Based Mix Networks: Modeling and Analysis

Anonymity technologies such as mix networks have gained increasing attention as a way to provide communication privacy. Mix networks were developed for message-based applications such as e-mail, but researchers have adapted mix techniques to low-latency flow-based applications such as anonymous Web browsing. Although a significant effort has been directed at discovering attacks against anonymity networks and developing countermeasures to those attacks, there is little systematic analysis of the quality of service (QoS) for such security and privacy systems. In this paper, we systematically address TCP performance issues of flow-based mix networks. A mix's batching and reordering schemes can dramatically reduce TCP throughput due to out-of-order packet delivery. We developed a theoretical model to analyze such impact and present formulas for approximate TCP throughput in mix networks. To improve TCP performance, we examined the approach of increasing TCP's duplicate threshold parameter and derived formulas for the performance gains. Our proposed approaches will not degrade the system anonymity degree since they do not change the underlying anonymity mechanism. Our data matched our theoretical analysis well. Our developed theoretical model can guide the deployment of batching and reordering schemes in flow-based mix networks and can also be used to investigate a broad range of reordering schemes.

A New Approach to Improve TCP Performance over Asymmetric Networks

TCP performance issues in bandwidth asymmetric networks are investigated. Related works to improve TCP performance in bandwidth asymmetric networks are introduced and analyzed. A new approach to improve TCP performance in two way traffic over asymmetric networks is also proposed in this paper, which can further improve TCP performance by assigning the bandwidth rates over the reverse link dynamically. Simulation results show that the new scheme has better performance compared to existing algorithms in terms of good utilization of the existing resources and higher throughput. Ill. 7, bibl. 9 (in English; summaries in English, Russian and Lithuanian).

TCP performance issues over wireless links

This article discusses the problems arising when the TCP/IP protocol suite is used to provide Internet connectivity over existing and emerging wireless links. Due to the strong drive toward wireless Internet access through mobile terminals, these problems must be carefully studied in order to build improved systems. We review wireless link characteristics using wireless LANs and cellular communications systems as examples. We then outline the performance problems of the TCP/IP protocol suite when employed over those links, such as degraded TCP performance due to mistaking wireless errors for congestion. We present various proposals for solving these problems and examine their benefits and limitations. Finally, we consider the future evolution of wireless systems and the challenges that emerging systems will impose on the Internet protocol suite.