An overview of DNS-based server selections in content distribution networks

With the explosive growth of the Internet, many new online services and applications are emerging. Some popular applications impose new challenges to the traditional Internet architecture and protocols. To alleviate the scalability burden in delivering popular Internet services to a large number of users, Web caching and content distribution technologies have been proposed, developed and deployed. Both approaches are designed to bring Web content closer to users and to improve their perceived quality of online experience. This paper surveys content distribution networks (CDNs), and in particular, their domain name system (DNS)-based server selection schemes. To bridge the gap between underlying principles and current practices, we choose a commercial content delivery provider, Akamai, as our focal case study. We first unveil Akamai's content delivery network, as well as its site and object delivery technologies. We then examine the DNS-based server selection schemes and their variants in detail. Moreover, we offer some performance insights and discussions on their built-in strengths and weaknesses that are also applicable to other CDN providers. (C) 2003 Elsevier B.V. All rights reserved