# Evaluation of Modern Internet Transport Protocols over GEO Satellite Links
## 2 Related Work  
The performance of TCP and QUIC protocols over satellite networks has been studied in numerous recent papers. The authors of [4] studied the QUIC protocol in a virtual  
Figure 1: Typical satellite link connection. testbed and recommended using Performance Enhancement Proxy (PEP) to enhance its performance in satellite networks. However, their results are sensitive to the CPU limitation of a single machine hosting a virtual testbed. On the other hand, the authors of [5] compared PEP for both QUIC and TCP in terrestrial and satellite networks, and found that the performance of both TCP and QUIC is enhanced by using PEP. Furthermore, the authors of [6] compared the performance of QUIC with TCP-PEP in satellite networks by using an experimental testbed. Using the throughput as a performance measurement, they found that the enhanced TCP-PEP outperforms QUIC in a lossy satellite link. They claim that QUIC needs a better loss recovery mechanism in the higher RTT and lossy networks. However, they did not specify which congestion control algorithm was used in their QUIC configuration. In [7], the authors examined the performance of TCP-PEP and different QUIC implementations (QUIC Chromimum, QUIC Apache, QUICKLY and NGTCP) over an experimental satellite testbed. The congestion control algorithms were Reno and Cubic. They found that QUICKLY outperforms the other QUIC implementations over satellite networks but the performance of all QUIC implementations is degraded with packet losses. The performance of QUIC with a recent congestion control algorithm called Bottleneck Bandwidth and Round-trip time (BBR) has been evaluated in [8], using an emulation testbed of satellite networks. Their preliminary evaluation indicated better results for QUIC with BBR compared to QUIC with Cubic. However, these papers did not investigate the perceived user-experience indicators which we are going to study in this paper. Also, the effects of acknowledgment overheads in QUIC over satellite networks have been evaluated using an emulated satellite testbed in [9]. It compared TCP with two different implementations of QUIC: QUICKLY-IETF-27 and Chromium- IETF -26. It found that the return link traffic on QUIC is larger than TCP due to the overhead of acknowledgments in QUIC. However, the congestion controls used in the experiments are different since Chromium used BBR, while TCP and QUICKLY used New Reno. This had a significant effect on performance. The authors of [10] evaluated, by simulation, the performance of HTTP/1.1 over TCP wave and standard TCP in terms of page load time with different web page sizes. They found that TCP wave performs better than standard TCP because it uses a burst-transmission paradigm instead of a window-based paradigm. Also, the performance of HTTP/2 over QUIC and TCP with Explicit Congestion Notification (ECN) was studied in [11] using an experimental testbed for an integrated space-terrestrial network. They evaluated the performance based on the page load time and the number of blocked messages. In their experiments, they found that HTTP/2 over QUIC with Cubic congestion control performed better than HTTP/2 over TCP with Cubic even with ECN enabled. The authors of [12] examined the performance of multiple satellite operators (Avanti, Astra and Tooway) in an experimental testbed with multiple HTTP protocols. They studied HTTP/1.1 and HTTP/2 over TCP, HTTP/1.1 and HTTP/2 over UDP, and HTTP/3 over QUIC with Cubic as the congestion control. They found that HTTP/1.1 outperforms other HTTP protocols. They also concluded that Performance Enhancement Proxies (PEPs) are necessary in satellite networks to enhance performance. However, the authors used Chromium to test the HTTP protocols which creates six fixed connections by default for HTTP/1.1 over TCP. As a result, HTTP/1.1 over TCP outperformed the other HTTP protocols in that paper. The authors of [13] addressed the challenges of using QUIC over satellite networks.