Song Xiao Lin Song Xiao Lin This document specifies a type of private networks that interconnect thin CPEs at multiple client sites by IP tunnels, or more specifically, lay over multiple client sites' Thin CPEs via IP tunnels. Those private overlay networks not only interconnect those sites by secure IP tunnels but can also enforce the client specified policies to govern how applications or hosts within those sites communicate and how to access public internet. Hosts or applications in those sites can be interconnected by Layer 2 networks or/and by Layer 3 networks. The network that the IP tunnels are traversing can be IPv4 or IPv6 networks. This document describes the special properties of the client defined networks over Thin CPEs. A separate draft will describes the special features that those IP tunnels need to have in order to interconnect multiple sites as if those sites are directly connected by wires and how communication policies are enforced.