Differential bandwidth allocation with multiplexed TCP connections

Abstract

This thesis presents and evaluates the design and implementation of a user-level library that performs bandwidth allocation among multiple application flows using multiple TCP connections. This work is motivated by emerging trends in network overlay applications to send multiple flows of data between machines. Existing approaches to manage the network either do not offer the control over network resources that these applications need, or are difficult to adopt. We present a novel user-level approach to this problem that uses multiple TCP connections, and we also present an evaluation of multiplexing strategies for the scheduler that multiplexes the multiple application flows onto the multiple TCP connections. We implemented and designed two scheduling algorithms, striping and pinning, to perform the multiplexing and evaluated them for various application behavior and various link characteristics through emulation. We describe how striping is preferred for applications that are not delay dependent, as well as applications that are not order dependent, while pinning is preferred for applications that are heavily memory constrained. Our results show that, for delay-constrained applications, links with low loss and low number of cross traffic favor the striping scheduler, while high loss or high numbers of cross traffic favor the pinning scheduler. Delay-constrained applications that maintain high number of flows also favor the pinning scheduler, while those that do not favor the striping scheduler. We conclude that a user-level approach is both feasible and preferred, and that both multiplexing approaches are viable options based on network characteristics and application behavior.