Low Earth Orbit (LEO) satellite networks such as Starlink allow global and affordable internet access. This not only connects remote residents, but also enables new potentials such as connecting non-stationary agricultural systems in rural areas for high-precision spot farming. One challenge is that tractors and farming robots need to transmit large amounts of data from cameras and laser scanners in real-time, which easily overwhelms the uplink capabilities of a single LEO connection. In this paper, we examine the Starlink performance of multiple terminals within a single service cell to lay ground for multipath link bundling as a possible approach to increase link capabilities. For this purpose, we present two measurement setups consisting of four and seven Starlink dishes placed in one service cell. We conduct multiple measurements and evaluate UDP and TCP throughput, latency, and packet loss. We find that UDP throughput scales almost linearly with the number of dishes, indicating significant bundling potential up to an expected limit. In contrast, TCP BBRv1’s bundling potential is limited, due to inefficiencies in utilizing the links. Moreover, we find that some packet loss events are synchronized within a service cell. For future and independent research, we make our dataset publicly available.

Low Earth Orbit (LEO) satellite networks like Starlink are susceptible to both external factors (e.g., weather and obstruction) and internal factors such as frequency and resource allocation changes. This causes performance instabilities by design. In this demo, we show that such instabilities can have a detrimental impact on the performance of TCP and consequently on large parts of today’s internet, as most traffic uses TCP as transport protocol. Consequently, LEO-specific adaptations to either TCP and/or higher-level applications are necessary.

This demo presents link ’em version 2, an open source modification of the Linux Network Emulator (netem), to enable trace-based loss and delay emulation of pre-recorded real-world network conditions. It is used in an experimental setup to demonstrate and evaluate the impact of Network Coding-based Forward Erasure Correction for TCP (TCPyNC) on the performance of Dynamic Adaptive Streaming over HTTP (DASH). Thus, the proposed demonstration showcases the novel features of link ’em v2 and highlights the capability of network coding-based FEC to improve the overall video quality and reduce stalling of DASH video streams.

TCP still is the prevailing transport protocol on the Internet. It does, however, suffer from severe performance issues on links with non-congestion losses. Instead of relying on the RTT-sensitive ARQ mechanism of TCP, network coding (NC) uses linear combinations of packets to correct forward erasures. Several approaches were developed to incorporate NC into TCP. While they are able to improve the offered service, their lack of deployability and fairness in modern environments is not desirable. To mitigate this, we propose TCPyNC, a Python-based intra-session NC user space shim layer for TCP. Not only are its gains equally high, but it is also more flexible regarding the use of TCP options and parameters. We use a numerical analysis and a testbed evaluation to determine parameters that enable a fair use of TCP in conjunction with Forward Erasure Correction (FEC). In order to reach this goal, we found the maxim less is more to be a sensible orientation. For scenarios with 10% random loss, instead of choosing a high redundancy rate and a large generation size in order to gain the best loss reduction, choosing redundancy rates that leave between 1% and 6% loss for TCP’s ARQ to correct and generation sizes below 32 when using default TCP parameters, yields fair results.