A Brief History of MPLS Usage in IPv6

Recent researches have stated the fast deployment of IPv6. It has been demonstrated that IPv6 grows much faster, being so more and more adopted by both Internet service providers but also by servers and end-hosts. In parallel, researches have been conducted to discover and assess the usage of MPLS tunnels. Indeed, recent developments in the ICMP protocol make certain
categories of MPLS tunnels transparent to traceroute probing. However, these studies focus only on IPv4, where MPLS is strongly deployed.

In this paper, we provide a first look at how MPLS is used under IPv6 networks using traceroute data collected by CAIDA. We have observed, at the first glance, that the MPLS deployment and usage seem to greatly differ between IPv4 and IPv6, in particular in the way MPLS label stacks are used. While label stacks are not that frequent in IPv4 (and mostly correspond to a VPN usage), they are prevalent in IPv6.  However, after a deeper look at the label stack typical content in IPv6, we understand that 2-label stack tunnels are mainly used for dual stack 6PE tunnels and ECMP load sharing purpose.  The technical deployment of such tunnels is really similar to VPN in practice but the objective is not the same (they are standard tunnels made with the IPv4 LDP for carrying IPv6 traffic).