Accessing websites via IPv6 is not only comparable in speed to IPv4, but is actually faster when visiting one in five of the world's most popular sites, according to German researchers.

In a new paper, Vaibhav Bajpai and Jürgen Schönwälder from the University of Bremen looked at the response times for the internet's top 10,000 most-visited websites (according to Alexa) over both IPv4 and IPv6, and concluded that not only have earlier delays been removed in the newer internet protocol, but that a connection is sometimes faster.

Although IPv4 connections remained faster the vast majority of the time, the researchers noted that in those cases they were rarely more than 1ms slower; ie, the difference was negligible.

The paper's abstract reads:

Using a three-years long (2013 to 2016) dataset, we show that TCP connect times to popular websites over IPv6 have considerably improved over time. As of May 2016, 18 per cent of these websites are faster over IPv6 with 91 per cent of the rest at most 1 ms slower.

That is a significant improvement from just a few years ago when IPv6 connections were often so slow that browsers actually timed out, which itself added yet one more reason for people not to transition their networks and systems to the incompatible protocol.

As the paper notes, much of the problem was attributed to two technologies that were intended to assist in shifting traffic from IPv4 to IPv6: the Teredo automatic tunneling technology and 6to4 relays. In both cases, the technologies added "noticeable latency" to connections.

In 2013, Microsoft announced it would stop using Teredo on Windows and would kill off its Teredo servers the following year. In 2015, the 6to4 prefix was phased out. The researchers noted – using data from 2013 to 2016 – that the result was a significant increase in speed over IPv6, with Teredo/6to4 now only being used for 0.01 per cent of traffic.

Fail whale

Other research has shown a huge drop in IPv6 failure rates, from 40 per cent in 2011 to 3.5 per cent in 2015. Still a significant amount, but no longer a barrier to adoption.

What is interesting to note is that some browsers actually favor the use of IPv6 over IPv4 and include a timer to decide whether to shift over to IPv4. Firefox and Opera used parallel TCP connections over both IPv4 and IPv6, but Apple uses a 25ms timer in favor of IPv6 and Google used a 300ms timer in its Chrome browser.

The researcher used the "Happy Eyeballs" (also known as Fast Fallback) algorithm developed by the Internet Engineering Task Force in 2012 (see RFC 6555) to gather their data. The algorithm gets applications to request both IPv4 and IPv6 connections and then connects using whichever comes back first. The timer can be used to give one a small handicap; by default Happy Eyeballs gives IPv6 a 300ms advantage.

As to which websites were actually faster over IPv6: out of the most well known, Netflix leads the way, followed by Yahoo, with YouTube and Google behind them. Facebook, Wikipedia and Microsoft basically run at the same speed regardless of protocol.

Despite the good news that the internet's future protocol is increasingly keeping up with its current ubiquitous one, there are still pockets of trouble: the researchers note than in one per cent of the 10,000 top websites on the internet, the IPv6 delay was still over 100ms.

A presentation of the paper recorded at a recent conference is available online. ®