a dynamic collection of network nodes that act as a subset of the entire collection of nodes in the network

a layer of virtual network topology on top of the physical network, which directly interfaces to users

an isolated virtual network deployed over an existing network

a term from computer science that describes a virtual and often semantically based indexing system that rides on top of physical network

a virtual network topology constructed on top of the Internet structure

a virtual topology constructed on top of the Internet infrastructure

A high-performance digital network that interconnects with the main public network but which has its own lines, exchanges, and, often, a separate international gateway.

An overlay network is a computer network which is built on top of another network. Nodes in the overlay can be thought of as being connected by virtual or logical links, each of which corresponds to a path, perhaps through many physical links, in the underlying network. For example, many peer-to-peer networks are overlay networks because they run on top of the Internet.