LINC: An In-Network Coding Approach to Tame Packet Loss in Hybrid Wireless-Fiber Backbones

Abstract: The emergence of ultra-low latency applications, such as financial transactions, has driven the development of hybrid backbone networks that rely on fiber, satellite, and microwave links. Despite providing low latencies, these hybrid networks suffer from occasional environmental packet loss caused by poor weather, construction, and line of sight blockage. Paradoxically, today's hybrid backbones rely on conventional transport protocols that take packet loss to signal network congestion, as opposed to transient environmental obstacles. A common approach to address this challenge is to use network coding (NC) between the end hosts to recover from these occasional packet loss events. However, current NC proposals assume full access to the end-hosts' stack to perform end-to-end encoding/decoding operations. In this paper, we introduce LINC, a novel system that provides in-network NC capabilities to mitigate environmental packet loss events without requiring cooperation from the end hosts. LINC uses a systematic block coding approach on a link-by-link basis, encoding and decoding packets inside the network. We model the tradeoff in goodput between end-to-end retransmissions and redundant packets introduced by LINC, and propose an optimization formulation to determine the optimal choice of coding parameters. Our simulations on real-world backbone topologies demonstrate that LINC reduces the end-to-end latency by up to 18% by eliminating unnecessary retransmissions.