Reblogged from CCIE, the beginning!:

6VPE is an easy solution to connect IPv6 customers through an existing stable IPv4 MPLS infrastructure.
All clients have to do is to connect to a Provider Edge (configured with IPv6 VRFs) using IPv6.
I hope this post will provide you with a brief and concise explanation about 6VPE.
Let’s start with a short animation resuming the 6VPE forwarding process: