Networking Investigate

The Delay-Friendliness of TCP

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Executive Summary

TCP has traditionally been considered unfriendly for real-time applications. Nonetheless, popular applications such as Skype use TCP since UDP packets cannot pass through many NATs and firewalls. This paper develops an analytical performance model for the delay of TCP. It uses extensive experiments to validate the model and to evaluate the impact of various TCP mechanisms on its delay performance. Based on the results, the working region for VoIP and live video streaming applications is derived and provide guidelines for delay-friendly TCP settings. This research indicates that simple application-level schemes, such as packet splitting and parallel connections, can reduce the delay of real-time TCP flows by as much as 30% and 90%, respectively.

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