Victor Ramiro

STEPS - an approach for human mobility modeling

In this paper we introduce Spatio-TEmporal Parametric Stepping (STEPS) - a simple parametric mobility model which can cover a large spectrum of human mobility patterns. STEPS makes abstraction of spatio-temporal preferences in human mobility by using a power law to rule the nodes movement. Nodes in STEPS have preferential attachment to favorite locations where they spend most of their time. Via simulations, we show that STEPS is able, not only to express the peer to peer properties such as inter-contact/contact time and to reflect accurately realistic routing performance, but also to express the structural properties of the underlying interaction graph such as small-world phenomenon. Moreover, STEPS is easy to implement, flexible to configure and also theoretically tractable.

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.

Pervasive Intelligent Routing in Content Centric Delay Tolerant Networks

This paper introduces a Swarm-Intelligence based Routing protocol (SIR) that aims to efficiently route information in content centric Delay Tolerant Networks (CCDTN) also dubbed pocket switched networks. First, this paper formalizes the notion of optimal path in CCDTN and introduces an original and efficient algorithm to process these paths in dynamic graphs. The properties and some invariant features of these optimal paths are analyzed and derived from several real traces. Then, this paper shows how optimal path in CCDTN can be found and used from a fully distributed swarm-intelligence based approach of which the global intelligent behavior (i.e. shortest path discovery and use) emerges from simple peer to peer interactions applied during opportunistic contacts. This leads to the definition of the SIR routing protocol of which the consistency, efficiency and performances are demonstrated from intensive representative simulations.

Swarm-based intelligent routing (SIR): a new approach for efficient routing in content centric delay tolerant networks

This paper introduces Swarm-based Intelligent Routing (SIR), a swarm intelligence based approach used for routing content in content centric Pocket Switched Networks. We first formalize the notion of optimal path in DTN, then introduce a swarm intelligence based routing protocol adapted to content centric DTN that use a publish/subscribe communication paradigm. The protocol works in a fully decentralized way in which nodes do not have any knowledge about the global topology. Nodes, via opportunistic contacts, update utility functions which synthesizes their spatio-temporal proximity from the content subscribers. This individual behavior applied by each node leads to the collective formation of gradient fields between content subscribers and content providers. Therefore, content routing simply sums up to follow the steepest slope along these gradient fields to reach subscribers who are located at the minima of the field. Via real traces analysis and simulation, we demonstrate the existence and relevance of such gradient field and show routing performance improvements when compared to classical routing protocols previously defined for information routing in DTN.

Temporal random walk as a lightweight communication infrastructure for opportunistic networks

This paper explores the idea of sharing a common storage unit (token) as a lightweight communication infrastructure for opportunistic networks. Instead of using contacts as opportunities to transfer messages, we use them to pass the token over time. We implement a Temporal Random Walk (TRW) process to support such evolution. Sending a message is equivalent to copying it in the token and passing the token to a connected node. Eventually the recipient node will get the token and all its addressed messages. We study our approach using both synthetic and real traces. We show that it can be equivalent to common routing strategies in terms of delivery ratio and delay.

On the limits of DTN monitoring

Compared to wired networks, Delay/Disruption Tolerant Networks (DTN) are challenging to monitor due to their lack of infrastructure and the absence of end-to-end paths. This work studies the feasibility, limits and convergence of monitoring such DTNs. More specifically, we focus on the efficient monitoring of intercontact time distribution (ICT) between DTN participants. Our contribution is two-fold. First we propose two schemes to sample data using monitors deployed within the DTN. In particular, we sample and estimate the ICT distribution. Second, we evaluate this scheme over both simulated DTN networks and real DTN traces. Our initial results show that (i) there is a high correlation between the quality of sampling and the sampled mobility type, and (ii) the number and placement of monitors impact the estimation of the ICT distribution of the whole DTN.

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.

HINT: from network characterization to opportunistic applications

The increasing trend on wireless-connected devices makes opportunistic networking a promising alternative to existing infrastructure-based networks. However, these networks offer no guarantees about connection availability or network topology. The development of opportunistic applications, i.e., applications running over opportunistic networks, is still in early stages. One of the reasons is a lack of tools to support this process. Indeed, many tools have been introduced to study and characterize opportunistic networks but none of them is focused on helping developers to conceive opportunistic applications. In this paper, we argue that the gap between opportunistic applications development and network characterization can be filled with network emulation. As proof of concept, we propose and describe HINT, a realtime event-driven emulator that allows developers to early test their opportunistic applications prior to deployment. We introduce the architecture and corresponding implementation of our proposal, and conduct a preliminary validation by assessing its scalability.

Using the HINT network emulator to develop opportunistic applications: demo

In this work, we show how to use HINT, a real-time event-driven network emulator, to support the development process of opportunistic applications. In this demo, we use this emulator in conjunction with an example Android chat application to demonstrate its features.

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.