A Network Operator Perspective on IPv6: Traffic Growth by the Numbers

Editor’s Note: This is a guest blog post by Martin Gysi. He is a Technical Cluster Leader at Swisscom.

When an Internet Service Provider turns on IPv6, what amount of IPv6 traffic can it expect? And what kind of traffic? At Swisscom, the largest ISP in Switzerland with a customer base of 1.8 million residential wireline broadband users, large-scale rollout of IPv6 to residential customers began in March 2013. A firmware update prepared a part of the installed customer router base with firmware that supported IPv6. By running a policy on our TR-69 provisioning system, we activated IPv6 over just a few nights.

Right now, 35% of our customers are running IPv6-enabled routers. The IPv6 traffic that they generate accounts for 8.5% of total traffic at peak time (which is at 21:00). Taking the average over an entire day, the share of IPv6 is slightly lower at 7.4%.

Taking only the subset of customers that have activated IPv6, what is the v6-ratio there? In March 2013, 16% of the traffic of those customers was using IPv6. Today, one year later, 24% of the traffic runs over IPv6, after oscillating around 20% for much of the second half of 2013.

While overall traffic is constantly growing, IPv6 traffic is growing at a faster rate: Since March 2013, IPv4 traffic per customer has increased by 20%. In the same period of time, IPv6 traffic per customer has increased by 98%!

Where does this traffic come from? Looking at the Alexa list of Switzerland’s most visited websites, you see that the top six sites all support IPv6. Google is present with three of its sites,, and And indeed, 60% of the total IPv6 traffic originates at a Google service, with YouTube being the main contributor. Facebook and Akamai are two other important sources of IPv6 traffic.

Most of the IPv6 traffic that we see is originating from a few, very large sources. The sources use Content Delivery Networks (CDNs) that are directly attached to our core networks. As a consequence, only a minority of the IPv6 traffic comes in from the “big-I” Internet. So while it is relatively easy to get to 20% of IPv6 traffic, the remaining 80% will be more challenging: Much work still lies ahead of us until the myriad of smaller services become available over IPv6 too. But growth is strong and promising.