On the responsiveness of DNS-based network control

Abstract

For the last few years, large Web content providers interested in improving their scalability and availability have increasingly turned to three techniques: mirroring, content distribution, and ISP multi-homing. The Domain Name System (DNS) has gained a prominent role in the way each of these techniques directs client requests to achieve the goals of scalability and availability. The DNS is thought to offer the transparent and agile control necessary to react quickly to ISP link failures or phenomenon such as flash crowds. In this paper, we investigate this assumption with the objective of quantifying the degree of responsiveness that can be expected from DNS. We use a combination of Web and DNS access measurements from several busy Web sites, as well as a large content distribution network, to characterize the behavior of end-systems and local DNS servers in terms of their adherence to DNS-based controls. Our results suggest that DNS is at best a coarse-grained mechanism, and poorly suited for applications, such as route control, which require quick response to link failures or performance degradations. We then propose several proactive techniques that, when deployed in cooperation between large content providers and important clients, have the potential to improve the responsiveness of DNS-based control. Copyright 2004 ACM.