Category Archives: CCR April 2020

An Artifact Evaluation of NDP

Noa Zilberman


Artifact badging aims to rank the quality of submitted research artifacts and promote reproducibility. However, artifact badging may not indicate inherent design and evaluation limitations.

This work explores current limits in artifact badging using a performance-based evaluation of the NDP artifact. We evaluate the NDP artifact beyond the Reusable badge’s level, investigating the effect of aspects such as packet size and random-number seed on throughput and flow completion time.

Our evaluation demonstrates that while the NDP artifact is reusable, it is not robust, and we identify architectural, implementation and evaluation limitations.

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An Open Platform to Teach How the Internet Practically Works

Thomas Holterbach, Tobias Bü, Tino Rellstab, Laurent Vanbever


Each year at ETH Zurich, around 100 students collectively build and operate their very own Internet infrastructure composed of hundreds of routers and dozens of Autonomous Systems (ASes). Their goal? Enabling Internet-wide connectivity. We find this class-wide project to be invaluable in teaching our students how the Internet infrastructure practically works. Among others, our students have a much deeper understanding of Internet operations alongside their pitfalls. Besides students tend to love the project: clearly the fact that all of them need to cooperate for the entire Internet to work is empowering. In this paper, we describe the overall design of our teaching platform, how we use it, and interesting lessons we have learnt over the years. We also make our platform openly available.

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Workshop on Internet Economics (WIE 2019) report

kc claffy, David Clark


On 9-11 December 2019, CAIDA hosted the 10th interdisciplinary Workshop on Internet Economics (WIE) at UC San Diego’s Supercomputer Center. This workshop series provides a forum for researchers, Internet facilities and service providers, technologists, economists, theorists, policymakers, and other stakeholders to exchange views on current and emerging economic and policy debates. This year’s meeting had a narrower focus than in years past, motivated by a new NSF-funded project being launched at CAIDA: KISMET (Knowledge of Internet Structure: Measurement, Epistemology, and Technology). The objective of the KISMET project is to improve the security and resilience of key Internet systems by collecting and curating infrastructure data in a form that facilitates query, integration and analysis. This project is a part of NSF’s new Convergence Accelerator program, which seeks to support fundamental scientific exploration by creating partnerships across public and private sectors to solve problems of national importance.

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Thoughts about Artifact Badging

Noa Zilberman, Andrew W. Moore


Reproducibility: the extent to which consistent results are obtained when an experiment is repeated, is important as a means to validate experimental results, promote integrity of research, and accelerate follow up work. Commitment to artifact reviewing and badging seeks to promote reproducibility and rank the quality of submitted artifacts.

However, as illustrated in this issue, the current badging scheme, with its focus upon an artifact being reusable, may not identify limitations of architecture, implementation, or evaluation.

We propose that to improve the insight into artifact reproducibility, the depth and nature of artifact evaluation must move beyond simply considering if an artifact is reusable. Artifact evaluation should consider the methods of that evaluation alongside the varying of inputs to that evaluation. To achieve this, we suggest an extension to the scope of artifact badging, and describe both approaches and best practice arising in other communities. We seek to promote conversation and make a call to action intended to strengthen the scientific method within our domain.

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Validating the Sharing Behavior and Latency Characteristics of the L4S Architecture

Dejene Boru Oljira, Karl-Johan Grinnemo, Anna Brunstrom, Javid Taheri


The strict low-latency requirements of applications such as virtual reality, online gaming, etc., can not be satisfied by the current Internet. This is due to the characteristics of classic TCP such as Reno and TCP Cubic which induce high queuing delays when used for capacity-seeking traffic, which in turn results in unpredictable latency. The Low Latency, Low Loss, Scalable throughput (L4S) architecture addresses this problem by combining scalable congestion controls such as DCTCP and TCP Prague with early congestion signalling from the network. It defines a Dual Queue Coupled (DQC) AQM that isolates low-latency traffic from the queuing delay of classic traffic while ensuring the safe co-existence of scalable and classic flows on the global Internet. In this paper, we benchmark the DualPI2 scheduler, a reference implementation of DQC AQM, to validate some of the experimental result(s) reported in the previous works that demonstrate the co-existence of scalable and classic congestion controls and its low-latency service. Our results validate the co-existence of scalable and classic flows using DualPI2 Single queue (SingleQ) AQM, and queue latency isolation of scalable flows using DualPI2 Dual queue (DualQ) AQM. However, the rate or window fairness between DCTCP without fair-queuing (FQ) pacing and TCP Cubic using DualPI2 DualQ AQM deviates from the original results. We attribute the difference in our results and the original results to the sensitivity of the L4S architecture to traffic bursts and the burst sending pattern of the Linux kernel.

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The web is still small after more than a decade

Nguyen Phong Hoang, Arian Akhavan Niaki, Michalis Polychronakis, Phillipa Gill


Understanding web co-location is essential for various reasons. For instance, it can help one to assess the collateral damage that denial-of-service attacks or IP-based blocking can cause to the availability of co-located web sites. However, it has been more than a decade since the first study was conducted in 2007. The Internet infrastructure has changed drastically since then, necessitating a renewed study to comprehend the nature of web co-location.

In this paper, we conduct an empirical study to revisit web co-location using datasets collected from active DNS measurements. Our results show that the web is still small and centralized to a handful of hosting providers. More specifically, we find that more than 60% of web sites are co-located with at least ten other web sites—a group comprising less popular web sites. In contrast, 17.5% of mostly popular web sites are served from their own servers.

Although a high degree of web co-location could make co-hosted sites vulnerable to DoS attacks, our findings show that it is an increasing trend to co-host many web sites and serve them from well-provisioned content delivery networks (CDN) of major providers that provide advanced DoS protection benefits. Regardless of the high degree of web co-location, our analyses of popular block lists indicate that IP-based blocking does not cause severe collateral damage as previously thought.

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Path persistence in the cloud: A study of the effects of inter-region traffic engineering in a large cloud provider’s network

Waleed Reda, Kirill Bogdanov, Alexandros Milolidakis, Hamid Ghasemirahni, Marco Chiesa, Gerald Q. Maguire, Dejan Kostić


A commonly held belief is that traffic engineering and routing changes are infrequent. However, based on our measurements over a number of years of traffic between data centers in one of the largest cloud provider’s networks, we found that it is common for flows to change paths at ten-second intervals or even faster. These frequent path and, consequently, latency variations can negatively impact the performance of cloud applications, specifically, latency-sensitive and geo-distributed applications.

Our recent measurements and analysis focused on observing path changes and latency variations between different Amazon AWS regions. To this end, we devised a path change detector that we validated using both ad hoc experiments and feedback from cloud networking experts. The results provide three main insights: (1) Traffic Engineering (TE) frequently moves (TCP and UDP) flows among network paths of different latency, (2) Flows experience unfair performance, where a subset of flows between two machines can suffer large latency penalties (up to 32% at the 95th percentile) or excessive number of latency changes, and (3) Tenants may have incentives to selfishly move traffic to low latency classes (to boost the performance of their applications). We showcase this third insight with an example using rsync synchronization.

To the best of our knowledge, this is the first paper to reveal the high frequency of TE activity within a large cloud provider’s network. Based on these observations, we expect our paper to spur discussions and future research on how cloud providers and their tenants can ultimately reconcile their independent and possibly conflicting objectives. Our data is publicly available for reproducibility and further analysis at

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RIPE IPmap Active Geolocation: Mechanism and Performance Evaluation

Ben Du, Massimo Candela, Bradley Huffaker, Alex C. Snoeren, kc claffy


RIPE IPmap is a multi-engine geolocation platform operated by the RIPE NCC. One of its engines, single-radius, uses active geolocation to infer the geographic coordinates of target IP addresses. In this paper, we first introduce the methodology of IPmap’s single-radius engine, then we evaluate its accuracy, coverage, and consistency, and compare its results with commercial geolocation databases. We found that 80.3% of single-radius results have city-level accuracy for our ground truth dataset, and 87.0% have city-level consistency when geolocating different interfaces on the same routers. Single radius provided geolocation inferences for 78.5% of 26,559 core infrastructure IP addresses from our coverage evaluation dataset. The main contributions of this paper are to introduce and evaluate the IPmap single-radius engine.

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The April 2020 Issue

SIGCOMM Computer Communication Review (CCR) is produced by a group of members of our community that spend time to prepare the newsletter that you read every quarter. Olivier Bonaventure served as editor during the last four years and his term is now over. It is my pleasure to now serve the community as the editor of CCR. As Olivier and other editors in the past did, we’ll probably adjust the newsletter to the evolving needs of the community. A first change is the introduction of a new Education series led by Matthew Caesar, our new SIGCOMM Education Director. This series will be part of every issue of CCR, and will contain different types of contributions, not only technical papers as in the current issue, but also position papers (that promote discussion through a defensible opinion on a topic), studies (describing research questions, methods, and results), experience reports (that describe an approach with a reflection on why it did/did not work), and approach reports (that describe a technical approach with enough detail for adoption by others).

This April 2020 issue contains five technical papers, the first paper of our new education series, as well as three editorial notes.

The first technical paper, RIPE IPmap Active Geolocation: Mechanism and Performance Evaluation, by Ben Du and his colleagues, introduces the research community to the IPmap single-radius engine and evaluates its effectiveness against commercial geolocation databases.

It is often believed that traffic engineering changes are rather infrequent. In the second paper, Path Persistence in the Cloud: A Study of the Effects of Inter-Region Traffic Engineering in a Large Cloud Provider’s Network, Waleed Reda and his colleagues reveal the high frequency of traffic engineering activity within a large cloud provider’s network.

In the third paper, The Web is Still Small After More Than a Decade, Nguyen Phong Hoang and his colleagues revisit some of the decade-old studies on web presence and co-location.

The fourth paper, a repeatable paper originated in the IMC reproducibility track, An Artifact Evaluation of NDP, by Noa Zilberman, provides an analysis of NDP (New Data centre protocol). NDP was first presented at ACM SIGCOMM 2017 (best paper award) and proposes a novel data centre transport architecture. In this paper, the author builds the analysis of the artefact proposed by the original authors of NDP, showing how it is possible to carry out research and build new results on previous work done by other fellow researchers.

The Low Latency, Low Loss, Scalable throughput (L4S) architecture addresses this problem by combining scalable congestion control such as DCTCP and TCP Prague with early congestion signalling from the network. In our fifth technical paper, Validating the Sharing Behavior and Latency Characteristics of the L4S Architecture, Dejene Boru Oljira and his colleagues validate some of the experimental result(s) reported in the previous works that demonstrate the co-existence of scalable and classic congestion controls and its low-latency service.

The sixth paper, also our very first paper in the new education series, An Open Platform to Teach How the Internet Practically Works, by Thomas Holterbach and his colleagues, describes a software infrastructure that can be used to teach about how the Internet works. The platform presented by the authors aims to be a much smaller, yet a representative copy of the Internet. The paper’s description and evaluation are focused on technical aspects of the design, but as a teaching tool, it may be more helpful to describe more about pedagogical issues.

Then, we have three very different editorial notes. The first, Workshop on Internet Economics (WIE 2019) report, by kc Klaffy and David Clark, reports on the 2019 interdisciplinary Workshop on Internet Economics (WIE). The second, strongly related to the fourth technical paper, deals with reproducibility. In Thoughts about Artifact Badging, Noa Zilberman and Andrew Moore illustrate that the current badging scheme may not identify limitations of architecture, implementation, or evaluation. Our last editorial note is a comment on a past editorial, “Datacenter Congestion Control: Identifying what is essential and making it practical” by Aisha Mushtaq, et al., from our July 2019 issue. This comment, authored by James Roberts, disputes that shortest remaining processing time (SRPT the crucial factor in achieving good flow completion time (FCT) performance in datacenter networks.

Steve Uhlig — CCR Editor