In the transition from IPv4 to IPv6, the preferred solution for network endpoints is to have both native IPv4 and IPv6 connectivity (also called dual-stack connectivity). If a site cannot get native IPv6 connectivity, however, the IPv4 network endpoints can choose from a number of conversion technologies to connect to the IPv6 Internet.

The most commonly used conversion mechanisms are 6to4, Teredo and tunnel-brokers. At recent RIPE meetings there have been claims that 6to4 connectivity is quite often broken. We were interested to find out how broken it really is.

The image below shows the percentage of 6to4 connections to our measurement machine that fail per day.

The failure rate is significant. During weekdays the failure rate is 15-20%. During weekends the failure rate is just below 10%.

This can have significant implications for Internet access providers, especially when IPv6-only content will become more common. Based on our measurements, IPv4-only customers will face significant problems reaching IPv6-only content using 6to4.

Considering the failure rate observed in this instance, it’s clear that using native IPv6 is certainly the preferred option going forward.

For more details about the methodology and the type of failures we observed, please refer to the article on RIPE Labs, “6to4 — How Bad is it Really?

Written by Mirjam Kuehne