Andreas Terzis
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An Internet-Wide Analysis of Traffic Policing
Tobias Flach
Luis Pedrosa
Tayeb Karim
Ethan Katz-Bassett
Ramesh Govindan
SIGCOMM (2016)
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Large flows like videos consume significant
bandwidth. Some ISPs actively manage these high volume
flows with techniques like policing, which enforces a flow
rate by dropping excess traffic. While the existence of policing
is well known, our contribution is an Internet-wide study
quantifying its prevalence and impact on video quality metrics.
We developed a heuristic to identify policing from
server-side traces and built a pipeline to deploy it at scale on
hundreds of servers worldwide within one of the largest online
content providers. Using a dataset of 270 billion packets
served to 28,400 client ASes, we find that, depending on region,
up to 7% of lossy transfers are policed. Loss rates are
on average 6× higher when a trace is policed, and it impacts
video playback quality. We show that alternatives to policing,
like pacing and shaping, can achieve traffic management
goals while avoiding the deleterious effects of policing.
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CQIC: Revisiting Cross-Layer Congestion Control f or Cellular Networks
Feng Lu
Hao Du
Geoffrey M. Voelker
Alex C. Snoeren
Proceedings of The 16th International Workshop on Mobile Computing Systems and Applications (HotMobile), ACM (2015), pp. 45-50
Preview abstract
With the advent of high-speed cellular access and the overwhelming popularity of smartphones, a large percent of today’s Internet content is being delivered via cellular links. Due to the nature of long-range wireless signal propagation, the capacity of the last hop cellular link can vary by orders of magnitude within a short period of time (e.g., a few seconds). Unfortunately, TCP does not perform well in such fast-changing environments, potentially leading to poor spectrum utilization and high end-to-end packet delay.
In this paper we revisit seminal work in cross-layer optimization the context of 4G cellular networks. Specifically, we leverage the rich physical layer information exchanged between base stations (NodeB) and mobile phones (UE) to predict the capacity of the underlying cellular link, and propose CQIC, a cross-layer congestion control design. Experiments on real cellular networks confirm that our capacity estimation method is both accurate and precise. A CQIC sender uses these capacity estimates to adjust its packet sending behavior. Our preliminary evaluation reveals that CQIC improves throughput over TCP by 1.08–2.89
× for small and medium flows. For large flows, CQIC attains throughput comparable to TCP while reducing the average RTT by 2.38–2.65x.
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Reducing Web Latency: the Virtue of Gentle Aggression
Tobias Flach
Barath Raghavan
Shuai Hao
Ethan Katz-Bassett
Ramesh Govindan
Proceedings of the ACM Conference of the Special Interest Group on Data Communication (SIGCOMM '13), ACM (2013)
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To serve users quickly, Web service providers build infrastructure closer to clients and use multi-stage transport connections. Although these changes reduce client-perceived round-trip times, TCP's current mechanisms fundamentally limit latency improvements. We performed a measurement study of a large Web service provider and found that, while connections with no loss complete close to the ideal latency of one round-trip time, TCP's timeout-driven recovery causes transfers with loss to take five times longer on average.
In this paper, we present the design of novel loss recovery mechanisms for TCP that judiciously use redundant transmissions to minimize timeout-driven recovery. Proactive, Reactive, and Corrective are three qualitatively different, easily-deployable mechanisms that (1) proactively recover from losses, (2) recover from them as quickly as possible, and (3) reconstruct packets to mask loss. Crucially, the mechanisms are compatible both with middleboxes and with TCP's existing congestion control and loss recovery. Our large-scale experiments on Google's production network that serves billions of flows demonstrate a 23% decrease in the mean and 47% in 99th percentile latency over today's TCP.
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packetdrill: Scriptable Network Stack Testing, from Sockets to Packets
Lawrence Brakmo
Matt Mathis
Barath Raghavan
Hsiao-keng Jerry Chu
Tom Herbert
Proceedings of the USENIX Annual Technical Conference (USENIX ATC 2013), USENIX, 2560 Ninth Street, Suite 215, Berkeley, CA, 94710 USA, pp. 213-218
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Testing today’s increasingly complex network protocol implementations can be a painstaking process. To help meet this challenge, we developed packetdrill, a portable, open-source scripting tool that enables testing the correctness and performance of entire TCP/UDP/IP network stack implementations, from the system call layer to the hardware network interface, for both IPv4 and IPv6. We describe the design and implementation of the tool, and our experiences using it to execute 657 test cases. The tool was instrumental in our development of three new features for Linux TCP—Early Retransmit, Fast Open, and Loss Probes—and allowed us to find and fix 10 bugs in Linux. Our team uses packetdrill in all phases of the development process for the kernel used in one of the world’s largest Linux installations.
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RACNet: a high-fidelity data center sensing network
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Chieh-Jan Mike Liang
Jie Liu
Liqian Luo
Feng Zhao
SenSys '09: Proceedings of the 7th ACM Conference on Embedded Networked Sensor Systems, ACM, New York, NY, USA (2009), pp. 15-28
Peeking Through the Cloud
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Fabian Monrose
Niels Provos
6th Conference on Applied Cryptography and Network Security (2008)
