QUIC Behavior over Dual Connectivity : Understanding QUIC throughput and fairness

Abstract: QUIC is a relatively new transport layer network protocol that has gained popularity over the last few years. The protocol was initially developed by Google and standardization work has been continued by the Internet Engineering Task Force (IETF) with the goal of it becoming the next generation transport protocol. While the standardization work is not yet finished, the protocol has seen a large adoption, already covering a large portion of the internet traffic. As a new protocol, many researchers have studied QUIC and compared it to TCP in typical scenarios. However, few studies have been performed on QUIC in specific scenarios. In this thesis, we present the first performance study of QUIC over Dual Connectivity (DC). DC is a multi-connectivity technique that allows users to connect to multiple cell towers with one user equipment. It is an important lower-layer feature accelerating the transition from 4G to 5G, which is also expected to play an important role in standalone 5G networks. With DC, higher throughput and reliability can be achieved by using multiple paths simultaneously. However, the drawback of DC is that it introduces packet reordering and jitter, which can significantly impact the performance of upper-layer protocols such as TCP and QUIC. To study the extent of this effect, a testbed is set up to evaluate QUIC over DC. Our performance evaluation compares the throughput of QUIC over DC with that of TCP over DC, and evaluates the fairness of QUIC over DC. Using a series of throughput and fairness experiments, we show how QUIC is affected by different DC parameters, network conditions, and whether the DC implementation aims to improve throughput or reliability. Our findings provide network operators with insights into understanding the impacts of splitting QUIC traffic in a DC environment. We show the value of increasing the UDP receive buffers when running QUIC over DC and that QUIC can utilize the increased bandwidth and reliability in DC, provided that the links' characteristics are similar. We also show that with reasonably selected DC parameters and increased UDP receive buffers, QUIC over DC performs similarly to TCP over DC and achieves optimal systemwide fairness under symmetric link conditions when DC is not used for packet duplication.