LOw-delay congestion control for REal-time applications over the iNternet
Congestion control in packet networks has been historically focused on avoiding network overload while providing full network utilization. The cornerstone result was the well-known TCP congestion and flow control algorithm proposed by Van Jacobson.
The goal of this project is to propose an algorithm that not only avoids network congestion while providing high utilization but also controls the network delay. Controlling the delay is of the utmost importance since the Internet is not only aimed at delay insensitive data traffic, but also at real-time communications (i.e. video chat, live streaming, virtual reality) and real-time control (i.e. autonomous driving, telerobotics, telesurgery).
Starting from the state of the art, the first goal will be to design the fundamental functions of the algorithm using a rigorous theoretical approach based on control theory so that algorithm properties such as stability and efficiency can be mathematically proven. The algorithm will be designed by taking into account both well-behaving wired connections and the new and more challenging 5G networks that have shown the need for a more responsive congestion control algorithm. In fact, recent literature has shown that the 5G link introduces fast on-off connectivity periods that, due to the high 5G bandwidth and the TCP cyclic probing phases, lead to high retransmission rates when using classic TCP (i.e., NewReno, Cubic, BBR).
The algorithm will be designed in accordance with the end-to-end principle. However, feedback and control functions implemented or envisaged in current and evolving networks will be also considered, namely: Software Defined Networks (SDN) functionalities, that can be used for traffic engineering, e.g., to steer aggregate traffic flows according to load balancing principles; local cross-layer optimization in 5G/6G context, with highly variable links and smart scheduling algorithms in the lower layers; in-band network telemetry functionalities.
The second goal will be to investigate the trade-off of implementing the end-to-end algorithms at the application layer over UDP or at the transport layer (TCP over IP) depending on target applications. Implementation at the application layer has the advantage that different algorithms can be designed and tuned for specific classes of applications having different requirements of delays and responsiveness.
The third goal will be to carry out an extensive experimental evaluation in two scenarios: (a) production networks, by leveraging an established collaboration with researchers at Google, aiming at contributing to the development of the WebRTC standard used for videoconferencing; (b) autonomous driving where mobile robots need to communicate with the infrastructure (f.i. a tracking system) or between them by exchanging data and audio/video channels.
