Conventional WAN technologies operate at the physical and data link layers of the OSI stack. This means that the WAN service provider does not take part in IP routing, but just carries IP packets from the source to the destination for the WAN that connects IP networks. The WAN infrastructure could be built using a private infrastructure or using a public infrastructure. It needs to be emphasized that although the WAN infrastructure is owned by the service providers (SPs), the SP operates at different layers of the OSI stack for different types of WAN. It is only a part of the infrastructure that is given to an enterprise for the right to use against a fee.
As an example, consider a transmission network infrastructure of a national service provider. That transmission infrastructure would consist of a large number of optical devices and multiplexers that would...