Impact of QUIC on fairness in mobile networks

Abstract

Transport protocols continuously evolve in order to meet the needs of users and new services. A recent significant example is Quick UDP Internet Connections (QUIC), an experimental protocol introduced by Google, that aims to replace two widely used transport and security protocols, namely Transmission Control Protocol (TCP) and Transport Layer Security (TLS). QUIC is implemented in user applications (rather than in the operating system’s kernel) and is meant to be resistant to ossification and therefore more versatile. Because of its evolvable nature, QUIC introduces new challenges in managing fairness. In this paper, we focus on determining the influence of QUIC on the data rate of mobile users. We specifically analyze protocol fairness when TCP and QUIC flows coexist on the wireless link of a mobile network. During our fairness assessments, we identified the impact of the following QUIC implementation aspects: the emulation of multiple TCP connections, the limitation of the congestion windows size and the usage of the hybrid start (hystart). Results show these mechanisms have a strong influence on fairness when the loss rate is low on the mobile network. Indeed, a wrong setting of the default parameters of these mechanisms or the activation of the hystart option can affect the performance of the transport protocols and therefore also the fairness. Finally, the lack of standardization of the emulation of multiple TCP connection in QUIC makes us question more broadly how QUIC’s design philosophy accommodates fairness.