Persistent DNS connections for improved performance

In the DNS resolution process, packet losses and ensuing retransmission timeouts induce marked latencies: the current UDP-based resolution process takes up to 5 seconds to detect a loss event. We find that persistent DNS connections based on TCP or TLS can provide an elegant solution to this problem. With controlled experiments on a testbed, we show that persistent DNS connections significantly reduces worst-case latency. We then leverage a large-scale platform to study the performance impact of TCP/TLS on recursive resolvers. We find that off-the-shelf software and reasonably powerful hardware can effectively provide recursive DNS service over TCP and TLS, with a manageable performance hit compared to UDP.