A virtual network is also called an overlay network.

The core philosophy of SD-WAN within the Huawei campus architecture is the decoupling of the Underlay (the physical transport network like MPLS, Internet, or 5G) from the Overlay (the virtualized service network). By using IPsec or VXLAN tunnels, SD-WAN creates a logical network where business policies—such as application-based routing and security rules—are applied. This allows enterprises to change their service logic without modifying the underlying physical WAN infrastructure.