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Geolocation of Internet hosts enables a diverse and interesting new class of location-aware applications. Previous measurement-based approaches use reference hosts, called landmarks, with a well-known geographic location to provide the location estimation of a target host. This leads to a discrete space of answers, limiting the number of possible location estimates to the number of adopted landmarks. In contrast, we propose Constraint-Based Geolocation (CBG), which infers the geographic location of Internet hosts using multilateration with distance constraints, thus establishing a continuous space of answers instead of a discrete one. CBG accurately transforms delay measurements to geographic distance constraints, and then uses multilateration to infer the geolocation of the target host. Our experimental results show that CBG outperforms the previous measurement-based geolocation techniques. Moreover, in contrast to previous approaches, our method is able to assign a confidence region to each given location estimate. This allows a location-aware application to assess whether the location estimate is sufficiently accurate for its needs.

Abstract. Location-aware applications require a geographic location service of Internet hosts. We focus on a measurement-based service for the geographic location of Internet hosts. Host locations are inferred by comparing delay patterns of geographically distributed landmarks, which are hosts with a known geographic location, with the delay pattern of the target host to be located. Results show a significant correlation between geographic distance and network delay that can be exploited for a coarse-grained geographic location of Internet hosts. 1

This article presents a characterization of the community Web of the people of Portugal. We defined criteria for delimiting this Web based on our past experience of crawling pages related to Portugal and collected over 3.2 million documents from 46,000 sites satisfying those criteria. Our characterization was derived from this crawl. We describe the rules that we established for defining the boundaries of this community Web and the methodology used to gather statistics. Statistics cover the number and domain distribution of sites; the number, type and size distribution of text documents; and the linkage structure of this Web. We also show how crawling constraints and abnormal situations on the Web can influence the statistics.

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The deployment of a geographic location service for Internet hosts enables a whole new class of location-aware applications. We focus on a technique that infers host locations using delay measurements to geographically distributed landmarks, which are hosts with a known geographic location. The problem we deal with is where to place such landmarks and the probe machines that perform the delay measurements. We propose a demographic placement approach to improve the representativeness of each landmark with respect to the hosts to be located. Results show that a relatively small number of landmarks are sufficient to cover the most part of hosts to be located. For a fixed number of landmarks, the demographic approach reduces the distances from most hosts to the nearest landmark. Considering the probe machines, we show that they have to be sparsely placed to avoid gathering redundant data.

Internet geolocation technology (IP geolocation) aims to determine the physical (geographic) location of Internet users and devices. It is currently proposed or in use for a wide variety of purposes, including targeted marketing, restricting digital content sales to authorized jurisdictions, and security applications such as reducing credit card fraud. This raises questions about the veracity of claims of accurate and reliable geolocation, and the ability to evade geolocation. We begin with a state-of-the-art survey of IP geolocation techniques and limitations, and examine the specific problems of (1) approximating a physical location from an IP address; and (2) approximating the physical location of an end client requesting content from a web server. In contrast to previous work, we consider also an adversarial model: a knowledgeable adversary seeking to evade geolocation. Our survey serves as the basis from which we examine tactics useful for evasion/circumvention. The adversarial model leads us to also consider the difficulty of (3) extracting the IP address of an end client visiting a server. As a side-result, in exploring the use of proxy servers as an evasionary tactic, to our surprise we found that we were able to extract an end-client IP address even for a browser protected by Tor/Privoxy (designed to anonymize browsing), provided Java is enabled. We expect our work to stimulate further open research and analysis of techniques for accurate and reliable IP geolocation, and also for evasion thereof. Our work is a small step towards a better understanding of what can, and cannot, be reliably hidden or discovered about IP addresses and physical locations of Internet users and machines. 1

This paper discusses user specific request redirection for personalizing responses to user requests in Content Delivery Networks (CDN). User specific request redirection refers to the process of redirecting user requests to a server on the content delivery network based on user specific information carried in the user request. Current redirection schemes in CDNs are either based on the authoritative DNS model or the URL rewrite model. The authoritative DNS model is not flexible to support user specific redirection as user specific information is not available to the DNS server; the URL rewrite model cannot support user specific redirection in practice because of the cost of on-the-fly URL rewrites required on a per user request basis. We discuss a technique that allows for flexible user specific request redirection. The technique is simple enough to be implemented at wire-speed in a switch.

A whole new class of location-aware services may be envisaged by the deployment of a geographic location service for Internet hosts. We focus on a technique that relies on delay measurements and the exploitation of a possible correlation between geographic distance and network delay. Our investigation shows that such a correlation becomes stronger as connectivity becomes richer. Host locations are inferred by comparing delay patterns of geographically distributed landmarks (hosts with a known geographic location) with the delay pattern of the target host to be located. The problem we deal with is how to best measure the similarity between the delay patterns of the landmarks and the one observed for the target host. The location estimation of the target host is the location of the landmark that presents the most similar delay pattern with respect to the one of the target host. We define and evaluate three similarity models. Experiments show that the previously adopted Euclidean distance is outperformed by other similarity models, resulting in a more accurate Internet host location from delay measurements.