Can Network Coding Mitigate TCP-induced Queue Oscillation on Narrowband Satellite Links?

Satellite-based Internet links often feature link bandwidths significantly below those of the ground networks on either side. This represents a considerable bottleneck for traffic between those networks. Excess traffic banks up at IP queues at the satellite gateways, which can prevent conventional TCP connections from reaching a transmission rate equilibrium. This well-known effect, known as queue oscillation can leave the satellite link severely underutilised, with a corresponding impact on the goodput of TCP connections across the link. Key to queue oscillation are sustained packet losses from queue overflow at the satellite gateway that the TCP senders cannot detect quickly due to the long satellite latency. Network-coded TCP (TCP/NC) can hide packet loss from TCP senders in such cases, allowing them to reach equilibrium. This paper reports on three scenarios in the Pacific with two geostationary and one medium earth orbit connection. We show by simulation and circumstantial evidence that queue oscillation is common, and demonstrate that tunneling TCP over network coding allows higher link utilisation.

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