Sigcomm: G: Behind the Curtain – The importance of replica selection in next generation networks

1. PROBLEM & MOTIVATION Smartdevices are becoming the primary or only Internet point of access for an ever larger fraction of users. Nearly a quarter of current web traffic is mobile, and recent industry studies have estimated a fourfold increase in global mobile data traffic by 2018, mainly driven by data demands and the growing number of smart phones and tablets [7]. Content delivery networks (CDNs) are responsible for delivering most of today’s Internet data. CDNs replicate popular content on servers worldwide and redirect users to “nearby” replica servers on demand. The Domain Name System (DNS) is instrumental in this process since CDN redirection, and thus the performance of content delivery, is typically based on the location of users’ DNS resolvers [21]. Considering the importance of content and the critical role of DNS for both name resolution and localization in today’s networks, it is somewhat surprising how little is known about the infrastructure and configuration of cell network DNS and its impact on content distribution. The 2011 study of Xu et al. [21] is today’s most comprehensive analysis of (the US) cellular network infrastructure, combining data from DNS logs, smartphone users and server logs. For the radio technologies in their study – 3G UTMS and EVDO – the authors point out the dominant role of radio latency and the limited number of network ingress points. They conclude that, in that setting, the best option for content providers is to locate servers close to these ingress points and that, given the restricted routing in these cellular networks, choosing content servers based on local DNS servers is sufficiently accurate. Independent of replica placement, current client redirection policy (i.e., replica selection) in mobile content delivery networks relies on similar heuristics to those used in the wired Internet, mapping clients’ IPs of their local-DNS servers (LDNS) to a network region [12, 13, 20], or through the use of anycast IP addresses.