Computer Science and Engineering, Department of


First Advisor

Lisong Xu

Date of this Version

Summer 8-2023

Document Type



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Computer Science, Under the Supervision of Professor Lisong Xu. Lincoln, Nebraska: August, 2023

Copyright © 2023 Mingrui Zhang


Transmission Control Protocol (TCP) is a fundamental Internet protocol responsible for controlling and coordinating the Internet traffic. As a result, TCP significantly influences the overall performance and stability of the Internet. One critical information required by a TCP connection to make decisions is FlightSize, which is the total amount of outstanding data contributed by the connection to the Internet. The FlightSize information is used by a TCP connection to determine its future sending rate and also avoid traffic congestion and collapse in the Internet. Consequently, an inaccurate estimation of FlightSize can result in degraded performance and instability of the Internet. However, this information must be estimated because direct access to it is not available to TCP. In this thesis, we present, to the best of our knowledge, the first comprehensive and accurate experimental study of the Linux FlightSize estimation method. 1) We design and develop the first evaluation platform where we can obtain the accurate FlightSize information and then evaluate the accuracy of Linux FlightSize estimation in various network conditions. 2) Using our platform, we find that the Linux FlightSize estimation method fails to accurately estimate FlightSize in many real-world network conditions of the Internet. These conditions include networks with packet loss, packet reordering, or timeout, and networks with high bandwidth and long distance. We also present an in-depth analysis of the reasons for the inaccuracy.

Adviser: Lisong Xu