During the past twenty years the Domain Name System (DNS) has sustained phenomenal growth while maintaining satisfactory performance. However, the original design focused mainly on system robustness against physical failures, and neglected the impact of operational errors such as misconfigurations. Our recent measurement effort revealed three specific types of misconfigurations in DNS today: lame delegation, diminished server redundancy, and cyclic zone dependency. Zones with configuration errors suffer from reduced availability and increased query delays up to an order of magnitude. Furthermore, while the original DNS design assumed that redundant DNS servers fail independently, our measurements show that operational choices made at individual zones can severely affect the availability of other zones. We found that, left unchecked, DNS configuration errors are widespread, with lame delegation affecting 15% of the DNS zones, diminished server redundancy being even more prevalent, and cyclic dependency appearing in 2% of the zones. We also noted that the degrees of misconfiguration vary from zone to zone, with most popular zones having the lowest percentage of errors. Our results indicate that DNS, as well as any other truly robust large-scale system, must include systematic checking mechanisms to cope with operational errors.

In this work we present the differences and similarities of the web browsing behavior in most common mobile platforms. We devise a novel Operating System (OS) fingerprinting methodology to distinguish different types of wireless devices (smartphone vs laptops) as well as operating system instances (iOS, Android, BlackBerry etc.). We showcase that most of the multimedia content in smartphone devices is delivered via Range-Requests, and a large portion of the video transfers are aborted. We also show that laptop devices have more intelligent browser caching capabilities. We investigate the impact of an additional browser cache, and demonstrate that a 10MB browser cache that is able to handle partial downloads in smartphones would be enough to handle the majority of the savings. Finally, we showcase that caching policies need to be amended to attain the maximum possible savings in proxy caches. Based on those optimizations the emulated proxy cache provides 10%-20% in bandwidth savings.