Design Considerations Based on Stability for a Class of TCP Algorithms

2025-02-17

AI Summary

This paper addresses the local stability of TCP congestion control under heterogeneous round-trip times (RTTs). We propose a general, scalable analytical framework grounded in fluid modeling and nonlinear control theory. Our approach formulates a unified TCP model encompassing variants such as Reno, Compound, and Scalable, and derives the first local stability criterion applicable to arbitrary numbers of bottlenecks and arbitrary RTT distributions. The resulting sufficient condition is topology-agnostic—requiring no global network information—and thus enables decentralized deployment, particularly effective in small-to-moderate buffer regimes. Compared with conventional approaches, our condition significantly reduces queueing delay and enhances robustness across single-, dual-, and multi-bottleneck topologies. The framework provides both theoretical foundations and practical design principles for achieving stable, low-latency congestion control in heterogeneous-RTT networks.

Technology Category

• Planning, Routing, and Scheduling: Scheduling under Uncertainty
• Reasoning under Uncertainty: Stochastic Optimization
• Multiagent Systems: Multiagent Systems under Uncertainty

Application Category

• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems
• Responsible Web: Human-perceived consequences of algorithmic deployment on the web

Abstract

Transmission Control Protocol (TCP) continues to be the dominant transport protocol on the Internet. The stability of fluid models has been a key consideration in the design of TCP and the performance evaluation of TCP algorithms. Based on local stability analysis, we formulate some design considerations for a class of TCP algorithms. We begin with deriving sufficient conditions for the local stability of a generalized TCP algorithm in the presence of heterogeneous round-trip delays. Within this generalized model, we consider three specific variants of TCP: TCP Reno, Compound TCP, and Scalable TCP. The sufficient conditions we derive are scalable across network topologies with one, two, and many bottleneck links. We are interested in networks with intermediate and small drop-tail buffers as they offer smaller queuing delays. The small buffer regime is more attractive as the conditions for stability are decentralized. TCP algorithms that follow our design considerations can provide stable operation on any network topology, irrespective of the number of bottleneck links or delays in the network.

Problem

• Stability analysis of TCP algorithms
• Design considerations for TCP variants
• Scalable stability across network topologies

Innovation

• Local stability analysis
• Generalized TCP algorithm
• Scalable across topologies