Implications of Netalyzr’s DNS Measurements

Netalyzr is a widely used network measurement and diagnosis tool. To date, it has collected 198,000 measurement sessions from 146,000 distinct IP addresses. One of the primary focus areas of Netalyzr is DNS behavior, including DNS resolver properties, common name lookups, NXDOMAIN wildcarding, lookup performance, and on-the-wire manipulations. Additional tests detect and categorize the behavior of any DNS proxies in the users’ gateways or firewalls. In this paper we report on DNS-specific insights from Netalyzr’s growing dataset. We identify significant problems in the existing DNS infrastructure, including unreliability of IP-level fragmentation, several kinds of result wildcarding, surprisingly poor lookup performance, and deliberate in-path DNS message manipulations. As these observations affect implementers of the DNS protocol as well as developers using common DNS APIs, we offer recommendations on common pitfalls and highlight likely impediments to the deployment of upcoming DNS technologies.