Design and implementation of a QUIC congestion control designed after TCP Hybla

The Internet architecture follows a multi-layered structure, in which each layer is associated with specific communication protocols. Standard Internet protocols work well for Earth-based networks, whereas satellite networks face challenges such as higher propagation times, increased loss rates due to attenuation and impairments, and link intermittancy due to node movement. Satellite networks use satellites to provide connectivity over vast geographic areas, and communicate with ground stations to control and relay transmissions. They differ based on the distance from Earth of the satellites involved: GEO (Geostationary Earth Orbit) satellites cover large areas thanks to their distance, and remain fixed relative to the Earth's surface, but suffer from high latency (with round-trip times over 600ms); LEO (Low Earth Orbit) satellites are closer, offering lower latency, but also reduced coverage and intermittent links due to higher orbital speeds. QUIC is a transport-level protocol originally developed by Google in 2012 as a TCP replacement in HTTP communications. This thesis, alongside two companion theses by fellow students Mattia Moffa and Luca Andreetti, is part of a project that seeks to evaluate QUIC’s performance in GEO and LEO satellite networks. The project was developed at the German Aerospace Center (DLR) near Munich, in collaboration with the University of Bologna. Congestion control regulates data transmission based on losses and latency. To address satellite network challenges, QUIC must use an appropriate congestion control algorithm. Algorithms designed for Earth-based networks may not perform well in satellite contexts; Hybla, on the other hand, proposed by C. Caini and R. Firrincieli in 2004 for TCP, is specifically designed to handle the long delays typical of GEO links. Thus, the object of this thesis is the implementation of a version of Hybla for QUIC, using Picoquic, an open-source implementation of the QUIC protocol.