overlay network

In tele- and data communications, an overlay network is a network that lies above another network. It decouples the tele and data services of the underlying network by encapsulating data packets or using tunneling.

Overlay networks can have broadband optical infrastructures; they can operate as proprietary networks within a regional area or as wide-area public networks. In the public domain, such a fiber network may consist of the access networks and the core network, which lies in a meshed structure over selected national and international cities.

Many overlay networks overlay the Internet, which in turn used the traditional long-distance telephone network infrastructure as an overlay research network. Other examples of overlay networks include virtual private networks( VPN), peer-to-peer networks( P2P), Internet telephony ( VoIP) and Internet television( IPTV), and software defined networks ( SDN). In terms of protocols, overlay networks work with Virtual Extensible LANs(VXLAN), Network Virtualization Using GRE( NVGRE) and others.