Javier Bustos-Jiménez

How AdkintunMobile measured the world

On this article we present the Adkintun Mobile Project: using passive monitors to measure the Quality of Service of Chilean Mobile Internet Providers, based on the metrics of antenna coverage and Internet connectivity. We present the main ideas, design decisions, development issues and setbacks of the project. Our contribution is to present to the readers the whole process of a project like this, which is based in volunteering and political decisions.

Miuz: measuring the impact of disconnecting a node

In this article we present Miuz, a robustness index for complex networks. Miuz measures the impact of disconnecting a node from the network while comparing the sizes of the remaining connected components. Strictly speaking, Miuz for a node is defined as the inverse of the size of the largest connected component divided by the sum of the sizes of the remaining ones. We tested our index in attack strategies where the nodes are disconnected in decreasing order of a specified metric. We considered Miuz and other well-known centrality measures such as betweenness, degree, and harmonic centrality. All of these metrics were compared regarding the behavior of the robustness (R- index) during the attacks. In an attempt to simulate the Internet backbone, the attacks were performed in complex networks with power-law degree distributions (scale-free networks). Preliminary results show that attacks based on disconnecting a few number of nodes Miuz are more dangerous (decreasing the robustness) than the same attacks based on other centrality measures. We believe that Miuz, as well as other measures based on the size of the largest connected component, provides a good addition to other robustness metrics for complex networks.

Adkintun: SLA Monitoring of ISP Broadband Offerings

Broadband Internet access has become a regular commodity on households around the world. For this reason, initiatives for characterization and monitoring of service offerings by Internet Service Providers (ISPs), by governments, researchers and independent entities have grown in popularity in the last few years. In this context, we present Adkintun, the Chilean initiative commanded by the Transports and Telecommunications Ministry (MTT) of Chile to NIC Chile Research Labs, in order to characterize the growing broadband Internet offer in that country providing an independent tool for consumers to monitor the effective quality of their provided service, and perform informed choices among chilean internet providers. In this article, we present the design, architecture and main results of Adkintun after a year of monitoring, measuring and characterizing chilean internet.

Mobile information visualization design of the adkintun mobile app

Mobile devices are becoming increasingly more powerful, offering new possibilities to collect, process, show, and interact with information visualization data directly on them. Despite the appearance of a plethora of mobile apps with clever InfoVis designs, particularly in the area of personal visualization (e.g., fitness, energy), surprisingly little research has been conducted on information visualization on mobile devices. In this paper, we explore information visualization on mobile devices by presenting a first design iteration and an initial evaluation of the Adkintun Mobile app, which measures the quality of service (QoS) of mobile Internet connections. Based on our findings, strategies to both assist people in making sense of data and designers in creating effective visualizations for mobiles are discussed.

Poor Man's Hardware Security Module (pmHSM): A Threshold Cryptographic Backend for DNSSEC

The DNS Security Extensions (DNSSEC) add a new layer of security based on public-key infrastructure: each DNS record is digitally signed to verify the authenticity of the answer. However, the introduction of DNSSEC has an impact in the operational workflow of DNS systems: (i) signatures have an expiration date, hence the records must be periodically signed and (ii) key management tasks can be overwhelming. These are problems specially for DNS zones with several records (for instance a Top Level Domain). The adoption of Hardware Security Module (HSM) is an option to provide highly secured keys and signature management. Nevertheless HSM is expensive and hardware can fail. We present a novel system based on threshold cryptography, called Poor Mans Hardware Security Module (pmHSM), which provides the signature components of an HSM over inexpensive commodity hardware to support the operational signing workflow of DNSSEC. This approach significantly improves security and availability of the overall system since the secret key is left beyond the reach of malicious compromises, it is spread among several independent nodes of the system.

Spin lock killed the performance star

The Internet has grown quite quickly, requiring more and more processing power each year to handle user requests in a timely fashion. In the multicore world, the addition of server-side threads should help improve server performance. However, several studies have shown that this is not true, identifying the Linux kernel as the possible culprit. Our working hypothesis is that the kernel does not provide a scalable interface for network communications. Through various tests, we narrowed the problem down to the implementation of the spin lock mechanism (a synchronization structure used mostly at the kernel level), which has been inherited from early versions of the Linux kernel. It is only now, with the emergence of multicore architectures, that users have begun to notice the performance hit that the existing spin lock implementation has on parallel systems, especially in multithreaded network protocols. Thus, our recommendation is that spin locks be redesigned so that the full power of multicore systems can be harnessed.

Co-creating visual overviews for open government data

In the last years governments have published multiple datasets on the Web. These datasets describe information about multiple areas, such as health, education and infrastructure. One risk of these Open Data initiatives is the creation of vacuous data portals ---similar as vacuous truths in logic--- where the publication of multiple datasets distract the publisher from publishing good, interesting and valuable datasets. One way to identify this risk consists in helping stakeholders to evaluate the quality and value of the datasets available. This is not an easy task, for many of such stakeholders may not have the technical skills to explore and analyze a dataset rapidly. In order to facilitate the rapid analysis and exploration of these datasets, we present our visual overviews, a visual approach for exploring datasets. These visual overviews were co-designed together with a series of stakeholders, taking into consideration their feedback and recommendations. We present a prototype and we describe the methodology used to create this tool.

Performance evaluation of streaming algorithms for network cameras

In this article we present the performance evaluation of different algorithms to distribute video frames from network cameras to multiple concurrent clients in real-time. The algorithms evaluated in this paper rely on a pool of buffers shared by all the clients. We implement these algorithms in the VLC media player and study their performance in terms of frame rate, hardware resource usage and decoding errors. Moreover, we compare their performance to the VLC streaming algorithm. Experimental results show that well designed algorithms combined with a sufficient number of buffers significantly outperform the VLC streaming algorithm.

Analysis of Linux UDP Sockets Concurrent Performance

Almost all DNS queries that traverse Internet are transported via UDP in self-contained small packages. Therefore, with no restriction of packet ordering, the intuition would say that adding thread-based parallelism to the servers will increase their performance, but it does not. This paper studies the problem of serialized access to UDP sockets, and states the problem in the way the packets are enqueued in the socket at kernel level, which introduces high levels of contention in synchronization primitives when using threads. As a naive solution, we present a multi-queue receiver network stack, which improves the performance of processing small UDP packages when multiple threads read from the same socket.

Mining Private Information from Public Data: The Transantiago Case

Transantiago, the smartcard-based public transportation system in Santiago, Chile, includes both a subway system and buses. An online information system lets card holders find detailed trip information, including start time and location, as well as frequency and type of transportation used, by simply providing its card ID. This article studies the privacy implications of the availability of the Transantiago online information system. The authors explore how much of a card holders information and behavior could be extracted from something as simple as their card ID. They concluded that, given that the corresponding card IDs are known, they can use simple statistical techniques to correctly predict the nearest public transport station to the homes of more than half of the users. This article is part of a special issue on pervasive analytics and citizen science.