Re-evaluating the responsiveness of DNS-based network control

For more than a decade, special purpose DNS [1] servers have been used to direct users to different IP addresses based on characteristics such as proximity, load balancing and failover. In this paper, we examine two of the mechanisms these special purpose DNS servers may use to control user traffic:-short time-to-lives (TTL) and time-splicing multiple responses. We find that although 2% of users are still using a stale DNS response after 15 minutes (despite a 20 second TTL), 90% of user requests will have switched to a new answer within 60 seconds. Further, when trying to direct users to two different locations in the ratio 90:10, we find time-splicing CNAME and A responses (corresponding to the two locations, respectively) is incompatible with a commonly deployed recursive resolver, and results in a ratio policy closer to 10:90. Overall we found that although DNS TTLs are not always respected, we are able manage load at a coarse granularity - provided time-spliced responses are of the same response type.