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## Observing the CenturyLink outage on 2020-08-30

CenturyLink / Level3 was reported to have a major outage on Sunday, 2020-08-30 (as reported on CNN and discussed on slashdot).

This outage was very clear in our Trinocular near-real-time outage detection system. We have summarized the details with images, before, during, and after, and an animation of the nearly 7-hour event or see the event on our near-real-time outage website.

This outage is one of the largest U.S. nation-wide events since the 2014-08-27 Time Warner outage.

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## new project “Detecting, Interpreting, and Validating from Outside, In, and Control, Disruptive Events” (DIVOICE)

We are happy to announce a new project, Detecting, Interpreting, and Validating from Outside, In, and Control, Disruptive Events (DIVOICE).

The DIVOICE project’s goal is to detect and understand Network/Internet Disruptive Events (NIDEs)—outages in the Internet.

We will work toward this goal by examining outages at multiple levels of the network: at the data plane, with tools such as Trinocular (developed at USC/ISI) and Disco (developed at IIJ); at the control plane, with tools such as BGPMon (developed at Colorado State University); and at the application layer.

We expect to improve methods of outage detection, validate the work against each other and external sources of information, and work towards attribution of outage root causes.

DIVOICE is a joint effort of the ANT Lab involving USC/ISI (PI: John Heidemann) and Colorado State University (PI: Craig Partridge).   DIVOICE builds on prior work on the LACANIC and Retro-Future Bridge and Outage projects.  DIVOICE is supported by the DHS HSARPA Cyber Security Division via contract number 70RSAT18CB0000014.

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## new conference paper “When the Dike Breaks: Dissecting DNS Defenses During DDoS” at ACM IMC 2018

We have published a new paper “When the Dike Breaks: Dissecting DNS Defenses During DDoS” in the ACM Internet Measurements Conference (IMC 2018) in Boston, Mass., USA.

From the abstract:

The Internet’s Domain Name System (DNS) is a frequent target of Distributed Denial-of-Service (DDoS) attacks, but such attacks have had very different outcomes—some attacks have disabled major public websites, while the external effects of other attacks have been minimal. While on one hand the DNS protocol is relatively simple, the \emph{system} has many moving parts, with multiple levels of caching and retries and replicated servers. This paper uses controlled experiments to examine how these mechanisms affect DNS resilience and latency, exploring both the client side’s DNS \emph{user experience}, and server-side traffic. We find that, for about 30\% of clients, caching is not effective. However, when caches are full they allow about half of clients to ride out server outages that last less than cache lifetimes, Caching and retries together allow up to half of the clients to tolerate DDoS attacks longer than cache lifetimes, with 90\% query loss, and almost all clients to tolerate attacks resulting in 50\% packet loss. While clients may get service during an attack, tail-latency increases for clients. For servers, retries during DDoS attacks increase normal traffic up to $8\times$. Our findings about caching and retries help explain why users see service outages from some real-world DDoS events, but minimal visible effects from others.

Datasets from this paper are available at no cost and are listed at https://ant.isi.edu/datasets/dns/#Moura18b_data.

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## new technical report “When the Dike Breaks: Dissecting DNS Defenses During DDoS (extended)”

We released a new technical report “When the Dike Breaks: Dissecting DNS Defenses During DDoS (extended)”, ISI-TR-725, available at https://www.isi.edu/~johnh/PAPERS/Moura18a.pdf.

From the abstract:

The Internet’s Domain Name System (DNS) is a frequent target of Distributed Denial-of-Service (DDoS) attacks, but such attacks have had very different outcomes—some attacks have disabled major public websites, while the external effects of other attacks have been minimal. While on one hand the DNS protocol is a relatively simple, the system has many moving parts, with multiple levels of caching and retries and replicated servers. This paper uses controlled experiments to examine how these mechanisms affect DNS resilience and latency, exploring both the client side’s DNS user experience, and server-side traffic. We find that, for about about 30% of clients, caching is not effective. However, when caches are full they allow about half of clients to ride out server outages, and caching and retries allow up to half of the clients to tolerate DDoS attacks that result in 90% query loss, and almost all clients to tolerate attacks resulting in 50% packet loss. The cost of such attacks to clients are greater median latency. For servers, retries during DDoS attacks increase normal traffic up to 8x. Our findings about caching and retries can explain why some real-world DDoS cause service outages for users while other large attacks have minimal visible effects.

Datasets from this paper are available at no cost and are listed at https://ant.isi.edu/datasets/dns/#Moura18a_data.

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## new talk “Internet Outages: Reliablity and Security” from U. of Oregon Cybersecurity Day 2018

John Heidemann gave the talk “Internet Outages: Reliablity and Security” at the University of Oregon Cybersecurity Day in Eugene, Oregon on April 23, 2018.  Slides are available at https://www.isi.edu/~johnh/PAPERS/Heidemann18e.pdf.

From the abstract:

The Internet is central to our lives, but we know astoundingly little about it. Even though many businesses and individuals depend on it, how reliable is the Internet? Do policies and practices make it better in some places than others?

Since 2006, we have been studying the public face of the Internet to answer these questions. We take regular censuses, probing the entire IPv4 Internet address space. For more than two years we have been observing Internet reliability through active probing with Trinocular outage detection, revealing the effects of the Internet due to natural disasters like Hurricanes from Sandy to Harvey and Maria, configuration errors that sometimes affect millions of customers, and political events where governments have intervened in Internet operation. This talk will describe how it is possible to observe Internet outages today and what they are beginning to say about the Internet and about the physical world.

This talk builds on research over the last decade in IPv4 censuses and outage detection and includes the work of many of my collaborators.

Data from this talk is all available; see links on the last slide.

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## new project “Interactive Internet Outages Visualization to Assess Disaster Recovery”

We are happy to announce a new project, Interactive Internet Outages Visualization to Assess Disaster Recovery.   This project is supporting the use of Internet outage measurements to help understand and recover from natural disasters. It will expand on the visualization of Internet outages found at https://ant.isi.edu/outage/world/.

This visualization was initially seeded by a Michael Keston research grant here at ISI, and the outage measurement techniques and ongoing data collection has been developed with the support of DHS (the LANDER-2007, LACREND, LACANIC, and Retro-future Bridge and Outages projects).

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## new website for browsing Internet outages

We are happy to announce a new website at https://ant.isi.edu/outage/world/ that supports our Internet outage data collected from Trinocular.

Our website supports browsing more than two years of outage data, organized by geography and time.  The map is a google-maps-style world map, with circle on it at even intervals (every 0.5 to 2 degrees of latitude and longitude, depending on the zoom level).  Circle sizes show how many /24 network blocks are out in that location, while circle colors show the percentage of outages, from blue (only a few percent) to red (approaching 100%).

We hope that this website makes our outage data more accessible to researchers and the public.

The raw data underlying this website is available on request, see our outage dataset webpage.

The research is funded by the Department of Homeland Security (DHS) Cyber Security Division (through the LACREND and Retro-Future Bridge and Outages projects) and Michael Keston, a real estate entrepreneur and philanthropist (through the Michael Keston Endowment).  Michael Keston helped support this the initial version of this website, and DHS has supported our outage data collection and algorithm development.

The website was developed by Dominik Staros, ISI web developer and owner of Imagine Web Consulting, based on data collected by ISI researcher Yuri Pradkin. It builds on prior work by Pradkin, Heidemann and USC’s Lin Quan in ISI’s Analysis of Network Traffic Lab.

ISI has featured our new website on the ISI news page.

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## new project LACANIC

We are happy to announce a new project, LACANIC, the Los Angeles/Colorado Application and Network Information Community.

The LACANIC project’s goal is to develop datasets to improve Internet security and readability. We distribute these datasets through the DHS IMPACT program.

As part of this work we:

• provide regular data collection to collect long-term, longitudinal data
• curate datasets for special events
• build websites and portals to help make data accessible to casual users
• develop new measurement approaches

We provide several types of datasets:

• anonymized packet headers and network flow data, often to document events like distributed denial-of-service (DDoS) attacks and regular traffic
• Internet censuses and surveys for IPv4 to document address usage
• Internet hitlists and histories, derived from IPv4 censuses, to support other topology studies
• application data, like DNS and Internet-of-Things mapping, to document regular traffic and DDoS events
• and we are developing other datasets

LACANIC allows us to continue some of the data collection we were doing as part of the LACREND project, as well as develop new methods and ways of sharing the data.

LACANIC is a joint effort of the ANT Lab involving USC/ISI (PI: John Heidemann) and Colorado State University (PI: Christos Papadopoulos).

We thank DHS’s Cyber Security Division for their continued support!

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## new talk “Digging in to Ground Truth in Network Measurements” at the TMA PhD School 2017

John Heidemann gave the talk “Digging in to Ground Truth in Network Measurements” at the TMA PhD School 2017 in Dublin, Ireland on June 19, 2017.  Slides are available at https://www.isi.edu/~johnh/PAPERS/Heidemann17c.pdf.
From the abstract:

New network measurements are great–you can learn about the whole world! But new network measurements are horrible–are you sure you learn about the world, and not about bugs in your code or approach? New scientific approaches must be tested and ultimately calibrated against ground truth. Yet ground truth about the Internet can be quite difficult—often network operators themselves do not know all the details of their network. This talk will explore the role of ground truth in network measurement: getting it when you can, alternatives when it’s imperfect, and what we learn when none is available.

This talk builds on research over the last decade with many people, and the slides include some discussion from the TMA PhD school audience.

Travel to the TMA PhD school was supported by ACM, ISI, and the DHS Retro-Future Bridge and Outages project.

Update 2017-07-05: The TMA folks have posted video of this “Ground Truth” talk to YouTube if you want to relive the glory of a warm afternoon in Dublin.

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## new conference paper “Does Anycast Hang up on You?” in TMA 2017

The paper “Does Anycast hang up on you?” will appear in the 2017 Conference on Network Traffic Measurement and Analysis (TMA) July 21-23, 2017 in Dublin, Ireland.

From the abstract:

Anycast-based services today are widely used commercially, with several major providers serving thousands of important websites. However, to our knowledge, there has been only limited study of how often anycast fails because routing changes interrupt connections between users and their current anycast site. While the commercial success of anycast CDNs means anycast usually work well, do some users end up shut out of anycast? In this paper we examine data from more than 9000 geographically distributed vantage points (VPs) to 11 anycast services to evaluate this question. Our contribution is the analysis of this data to provide the first quantification of this problem, and to explore where and why it occurs. We see that about 1\% of VPs are anycast unstable, reaching a different anycast site frequently (sometimes every query). Flips back and forth between two sites in 10 seconds are observed in selected experiments for given service and VPs. Moreover, we show that anycast instability is persistent for some VPs—a few VPs never see a stable connections to certain anycast services during a week or even longer. The vast majority of VPs only saw unstable routing towards one or two services instead of instability with all services, suggesting the cause of the instability lies somewhere in the path to the anycast sites. Finally, we point out that for highly-unstable VPs, their probability to hit a given site is constant, which means the flipping are happening at a fine granularity—per packet level, suggesting load balancing might be the cause to anycast routing flipping. Our findings confirm the common wisdom that anycast almost always works well, but provide evidence that a small number of locations in the Internet where specific anycast services are never stable.

This paper is joint work of Lan Wei and John Heidemann.  A pre-print of paper is at http://ant.isi.edu/~johnh/PAPERS/Wei17b.pdf, and the datasets from the paper are at https://ant.isi.edu/datasets/anycast/index.html#stability.