How Ready Is DNS for an IPv6-Only World?

TL;DR

This study examines DNS resolution issues in an IPv6-only environment, revealing significant centralization effects and identifying key operators impacting IPv6 readiness of zones.

Contribution

It highlights the challenges of IPv6-only DNS resolution, especially due to centralization and delegation chain issues, providing longitudinal insights into DNS IPv6 adoption.

Findings

A substantial fraction of zones cannot resolve in IPv6-only scenarios.

A small number of DNS providers influence most IPv6 resolution failures.

Enabling IPv6 glue records significantly improved IPv6 resolution over time.

Abstract

DNS is one of the core building blocks of the Internet. In this paper, we investigate DNS resolution in a strict IPv6-only scenario and find that a substantial fraction of zones cannot be resolved. We point out, that the presence of an AAAA resource record for a zone's nameserver does not necessarily imply that it is resolvable in an IPv6-only environment since the full DNS delegation chain must resolve via IPv6 as well. Hence, in an IPv6-only setting zones may experience an effect similar to what is commonly referred to as lame delegation. Our longitudinal study shows that the continuing centralization of the Internet has a large impact on IPv6 readiness, i.e., a small number of large DNS providers has, and still can, influence IPv6 readiness for a large number of zones. A single operator that enabled IPv6 DNS resolution -- by adding IPv6 glue records -- was responsible for around 20.3% of all zones in our dataset not resolving over IPv6 until January 2017. Even today, 10% of DNS operators are responsible for more than 97.5% of all zones that do not resolve using IPv6.