ABC: A Simple Explicit Congestion Controller for Wireless Networks

We propose Accel-Brake Control (ABC), a simple and deployable explicit congestion control protocol for network paths with time-varying wireless links. ABC routers mark each packet with an "accelerate" or "brake", which causes senders to slightly increase or decrease their congestion windows. Routers use this feedback to quickly guide senders towards a desired target rate. ABC requires no changes to header formats or user devices, but achieves better performance than XCP. ABC is also incrementally deployable; it operates correctly when the bottleneck is a non-ABC router, and can coexist with non-ABC traffic sharing the same bottleneck link. We evaluate ABC using a Wi-Fi implementation and trace-driven emulation of cellular links. ABC achieves 30-40% higher throughput than Cubic+Codel for similar delays, and 2.2X lower delays than BBR on a Wi-Fi path. On cellular network paths, ABC achieves 50% higher throughput than Cubic+Codel

Analysis of RED-Family Active Queue Management

RED is an Active Queue Management (AQM) technique that is intended to achieve high link utilization with a low queuing delay. Recent studies show that RED is difficult to configure for some rapidly changing traffic mixes and loads [1]. Other studies show that under some conditions, the performance gains of RED and its variants over traditional drop-tail queue management is not significant given the additional complexity required for proper configuration [2], [3]. Recent variants of RED, such as Adaptive- RED [4], are designed to provide more robust RED performance under a wider-range of traffic conditions. This paper develops a general queue law for TCP-RED control systems that use packet dropping and/or Explicit Congestion Notification (ECN) marking as congestion signaling methods, and illustrates the impact of TCP traffic on the behavior of congested router queue. Furthermore, this paper provides additional analysis of RED and newer variants of RED including Adaptive-RED [4] that is designed to provide more robust RED performance under a wider-range of traffic conditions. Through careful simulation designs using the queue law and analysis, this paper confirms that RED-like AQM techniques that employ packet dropping do not significantly improve performance over that of drop-tail queue management. However, when AQM techniques use ECN marking, the performance gains of AQM in terms of goodput and delay can be significant over that of drop-tail queue management

Why internet protocols need incentives

Internet routers are a commons. While modest regulatory measures have generally been successful for Information Communication Technologies (ICT), this paper argues that the lack of regulation has hindered the technological evolution of the Internet in some areas. This issue is examined through five Internet problems, and the technological solutions adopted. The key contribution of this paper is the explanation of these issues and the identification of areas where misaligned incentives promote inadequate solutions or inaction. The paper reviews the available measures to encourage the adoption of globally beneficial Internet technologies

Evaluation of the Impact of Packet Drops due to AQM over Capacity Limited Paths

Postprin

Measuring the State of ECN Readiness in Servers, Clients, and Routers

Proceedings of the Eleventh ACM SIGCOMM/USENIX Internet Measurement Conference (IMC 2011), Berlin, DE, November 2011.Better exposing congestion can improve traffic management in the wide-area, at peering points, among residential broadband connections, and in the data center. TCP's network utilization and efficiency depends on congestion information, while recent research proposes economic and policy models based on congestion. Such motivations have driven widespread support of Explicit Congestion Notification (ECN) in modern operating systems. We reappraise the Internet's ECN readiness, updating and extending previous measurements. Across large and diverse server populations, we find a three-fold increase in ECN support over prior studies. Using new methods, we characterize ECN within mobile infrastructure and at the client-side, populations previously unmeasured. Via large-scale path measurements, we find the ECN feedback loop failing in the core of the network 40\% of the time, typically at AS boundaries. Finally, we discover new examples of infrastructure violating ECN Internet standards, and discuss remaining impediments to running ECN while suggesting mechanisms to aid adoption

An Efficient Framework of Congestion Control for Next-Generation Networks

The success of the Internet can partly be attributed to the congestion control algorithm in the Transmission Control Protocol (TCP). However, with the tremendous increase in the diversity of networked systems and applications, TCP performance limitations are becoming increasingly problematic and the need for new transport protocol designs has become increasingly important.Prior research has focused on the design of either end-to-end protocols (e.g., CUBIC) that rely on implicit congestion signals such as loss and/or delay or network-based protocols (e.g., XCP) that use precise per-flow feedback from the network. While the former category of schemes haveperformance limitations, the latter are hard to deploy, can introduce high per-packet overhead, and open up new security challenges. This dissertation explores the middle ground between these designs and makes four contributions. First, we study the interplay between performance and feedback in congestion control protocols. We argue that congestion feedback in the form of aggregate load can provide the richness needed to meet the challenges of next-generation networks and applications. Second, we present the design, analysis, and evaluation of an efficient framework for congestion control called Binary Marking Congestion Control (BMCC). BMCC uses aggregate load feedback to achieve efficient and fair bandwidth allocations on high bandwidth-delaynetworks while minimizing packet loss rates and average queue length. BMCC reduces flow completiontimes by up to 4x over TCP and uses only the existing Explicit Congestion Notification bits.Next, we consider the incremental deployment of BMCC. We study the bandwidth sharing properties of BMCC and TCP over different partial deployment scenarios. We then present algorithms for ensuring safe co-existence of BMCC and TCP on the Internet. Finally, we consider the performance of BMCC over Wireless LANs. We show that the time-varying nature of the capacity of a WLAN can lead to significant performance issues for protocols that require capacity estimates for feedback computation. Using a simple model we characterize the capacity of a WLAN and propose the usage of the average service rate experienced by network layer packets as an estimate for capacity. Through extensive evaluation, we show that the resulting estimates provide good performance

End-to-End Congestion Control Schemes: Utility Functions, Random Losses and ECN Marks

We present a framework for designing end-to-end congestion control schemes in a network where each user may have a different utility function and may experience noncongestion-related losses. We first show that there exists an additive-increase-multiplicative-decrease scheme using only end-to-end measurable losses such that a socially optimal solution can be reached. We incorporate round-trip delay in this model, and show that one can generalize observations regarding TCP-type congestion avoidance to more general window flow control schemes. We then consider explicit congestion notification (ECN) as an alternate mechanism (instead of losses) for signaling congestion and show that ECN marking levels can be designed to nearly eliminate losses in the network by choosing the marking level independently for each node in the network. While the ECN marking level at each node may depend on the number of flows through the node, the appropriate marking level can be estimated using only aggregate flow measurements, i.e., per-flow measurements are not required