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Recent studies show that a significant part of Internet traffic is delivered through Web-based applications. To cope with the increasing demand for Web content, large scale content hosting and delivery infrastructures, such as data-centers and content distribution networks, are continuously being deployed. Being able to identify and classify such hosting infrastructures is helpful not only to content producers, content providers, and ISPs, but also to the research community at large. For example, to quantify the degree of hosting infrastructure deployment in the Internet or the replication of Web content.In this paper, we introduce Web Content Cartography, i.e., the identification and classification of content hosting and delivery infrastructures. We propose a lightweight and fully automated approach to discover hosting infrastructures based only on DNS measurements and BGP routing table snapshots. Our experimental results show that our approach is feasible even with a limited number of well-distributed vantage points. We find that some popular content is served exclusively from specific regions and ASes. Furthermore, our classification enables us to derive content-centric AS rankings that complement existing AS rankings and shed light on recent observations about shifts in inter-domain traffic and the AS topology.

Recently, webmail interfaces, e.g., Horde, Outlook Web Access, and webmail platforms such as GMail, Yahoo!, and Hotmail have seen a tremendous boost in popularity. Given the importance of e-mail for personal and business use alike, and its exposure to imminent threats, there exists the need for a comprehensive view of the Internet mail system, including webmail traffic. We, in this paper, propose a novel, passive approach to identify webmail traffic solely based on network-level data in order to obtain a comprehensive view of the mail system. Key to our approach is that we leverage correlations across protocols and time to introduce three novel features for HTTPS webmail classification. Our first feature is based on the finding that webmail servers tend to reside close to legacy mail servers, e.g. IMAP and POP, which can be easily identified. Our second feature leverages that the usage of webmail services results in distinct patterns on sessions' duration and on the diurnal/weekly traffic usage profile. In addition, our third feature exploits the observation that traffic flows to webmail platforms exhibit inherent periodicities due to the fact that AJAX-based clients periodically check for new messages. We use these three features to build a simple classifier and detect webmail traffic on real-world NetFlow traces from a medium-sized backbone network. We believe that the major contribution of this paper -- exploring a set of new features that could classify applications that run over HTTPS ports solely based on NetFlow data -- will stimulate more general advance in the field of traffic classification.

The Domain Name System (DNS) is a fundamental building block of the Internet. Today, the performance of more and more applications depend not only on the responsiveness of DNS, but also the exact answer returned by the queried DNS resolver, e.g., for Content Distribution Networks (CDN).In this paper, we compare local DNS resolvers against GoogleDNS and OpenDNS for a large set of vantage points. Our end-host measurements inside 50 commercial ISPs reveal that two aspects have a significant impact on responsiveness: (1) the latency to the DNS resolver, (2) the content of the DNS cache when the query is issued. We also observe significant diversity, even at the AS-level, among the answers provided by the studied DNS resolvers. We attribute this diversity to the location-awareness of CDNs as well as to the location of DNS resolvers that breaks the assumption made by CDNs about the vicinity of the end-user and its DNS resolver. Our findings pinpoint limitations within the DNS deployment of some ISPs, as well as the way third-party DNS resolvers bias DNS replies.