OrbCC: High-Throughput and Low-Latency Data Transport for LEO Satellite Networks

TL;DR

OrbCC is a novel transport protocol designed for LEO satellite networks that uses in-network congestion information to reduce latency, increase throughput, and handle dynamic network conditions effectively.

Contribution

OrbCC introduces in-network congestion support and adaptive control mechanisms tailored for the unique challenges of LEO satellite networks.

Findings

OrbCC significantly improves goodput over existing protocols.

OrbCC reduces latency and retransmissions in satellite network simulations.

OrbCC effectively responds to congestion hotspots and path changes.

Abstract

The highly dynamic nature of Low-Earth Orbit (LEO) satellite networks introduces challenges that existing transport protocols fail to address, including non-congestive latency variation and loss, transient congestion hotspots, and frequent handovers that cause temporary disconnections and route changes with unknown congestion and delay characteristics. Our contention is that with this increase in complexity, there is insufficient information being returned from the network for existing congestion control algorithms to minimise latency while maintaining high throughput and minimising retransmissions. Our approach, OrbCC, leverages in-network support to collect per-hop congestion information and uses it to (1) minimise buffer occupancy and end-user latency, (2) maximise application throughput and network utilisation, and (3) rapidly respond to congestion hotspots. We evaluate OrbCC against state-of-the-art transport protocols using OMNeT++/INET-based LEO satellite simulations and targeted micro-benchmarks. The simulations capture RTT dynamics in a LEO constellation, while the micro-benchmarks isolate key characteristics such as non-congestive latency variation and loss, path changes, and congestion hotspots. Results show that OrbCC significantly improves goodput while simultaneously reducing latency and retransmissions compared to existing approaches.