  NAT64 is an IPv6 transition mechanism that enables IPv6-only hosts to access
the IPv4 Internet. Understanding the deployment of NAT64, and its performance
impact, is crucial to the success of the IPv6 transition, by encouraging
IPv6-only deployments. We develop a set of tests for detecting NAT64 and apply
them to the RIPE Atlas testbed, finding 224 probes, in 43 networks, that can
use NAT64 to access the IPv4 Internet. Using 34 dual stack probes, that have
both NAT64 and native IPv4 access, to compare performance, we find that NAT64
paths are, on average, 23.13% longer, with 17.47% higher round-trip times.
