lements of hardware and software, supported and managed by a sophisticated network and equipment management infrastructure capable of moni- toring, detecting, and reporting network behavior and performance outside predetermined limits. Strictly speaking, a private network is built using the same or similar kinds of equipment, software, and supporting infrastructure. It requires capital investment and ongoing operations expense. In the same context, private networks are used exclusively by their owners and don't provide services or facilities to others. Satellite facilities are generally thought of as private networks; however, regardless of the term, they are built using shared and non- shared equipment. Public networks, also called common carrier networks, are shared among a community of enterprise and residential customers. They operate under rules and regulations promulgated by the Federal Communi- cations Commission (FCC) and state Public Utilities Commissions (PUCs), based on state and federal law in the United States, and similar 3 CONTENT TRANSPORT NETWORK DEFINED government bodies in other countries. This includes physical aspects of orbital platforms, radio frequency spectrum, and, to a lesser degree, the equipment and services in ground station facilities. Virtual private network (VPN) is a term used to describe a network designed and created from public network facilities and services. In some designs, the customer purchases or otherwise acquires the right to use equipment and software making up a VPN. Typically, this equipment is located on customer premises, although it may be co- located in service provider facilities with other customers or carrier owned equipment. VPNs didn't just show up yesterday. The incar- nation in the mid-1980s was software-defined network (SDN). These terms are another source of confusion. At a high level, both mean the same thing. Both evolved from private networks, which are built using point-to-point private line facilities and premises based multiplexing and switching e