2026-07-22T03:56:45Z https://drops.dagstuhl.de/oai

oai:drops-oai.dagstuhl.de:25593 2026-06-23T12:09:50Z ddc:004 open_access

Contracts: A Unified Lens on Congestion Control Robustness, Fairness, Congestion, and Generality Agarwal, Anup Arun, Venkat Seshan, Srinivasan Transport Protocols Congestion Control Fairness Congestion control algorithms (CCAs) operate in partially observable environments. They cannot directly observe link capacities or competing flows. To share network resources fairly, CCAs (implicitly) communicate fair shares through observable signals. For instance, Reno encodes the fair share as ∝ 1/√{loss rate}. We call such communication mechanisms as contracts. We find that the choice of contract fixes key steady-state performance metrics, including (1) robustness to errors in congestion signals, (2) fairness, (3) amount of congestion (e.g., delay, loss), and (4) generality (e.g., range of supported link rates). This leads to fundamental tradeoffs between these metrics. Further, we show that many contracts lead to starvation (extreme unfairness), and must be avoided. Hence, contracts are a powerful way to analyze tradeoffs and avoid pitfalls in CCA design and analysis. We empirically validate our findings and discuss their implications on CCA design and network measurement. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Anup Agarwal and Venkat Arun and Srinivasan Seshan 2026 Is Part Of OASIcs, Volume 139, 1st New Ideas in Networked Systems (NINeS 2026) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/OASIcs.NINeS.2026.8 urn:nbn:de:0030-drops-255933 https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.NINeS.2026.8 eng https://creativecommons.org/licenses/by/4.0/legalcode