20240419 - J. Gomez/U of SC - "Improving TCP Fairness in Non-programmable Networks using P4"

Authors:
Jose Gomez, Univ of South Carolina
Jorge Crichigno, Univ of South Carolina

Date:
April 19th, 2024

Title:
Improving TCP Fairness in Non-programmable Networks using P4-programmable Data Planes

Abstract:
This work presents a system that improves Transmission Control Protocol (TCP) fairness by reducing the impact of Round-trip Time (RTT) unfairness and rebalancing the router's queue. RTT unfairness arises in traditional loss-based Congestion Control Algorithms (CCAs) such as CUBIC when flows with shorter RTTs are favored with higher bandwidth shares compared to those with longer RTTs. Conversely, newer CCAs such as the Bottleneck Bandwidth and Round-trip Time (BBR) exhibit the opposite behavior, where flows with longer RTTs achieve higher throughput compared to those with shorter RTTs. The proposed system uses a P4-programmable Data Plane (PDP) as a measurement tool to process a copy of traffic from the link between two non-programmable routers. The PDP calculates the RTT and throughput of TCP flows and generates control rules to be implemented in a non-programmable router. These rules distribute TCP flows into separate queues based on the limits resulting from a classification algorithm that aims at minimizing the impact of RTT unfairness.

The results show the system's ability to improve fairness among competing flows and reduce the Flow Completion Time (FCT) of long flows regardless of the CCA. Moreover, the system is capable of measuring the throughput of individual flows and rebalancing the bandwidth allocation per queue. This approach ensures that the bandwidth that is not fully utilized can be effectively used by other flows.