A communications network managed by a commercial company that provides the primary high-speed links across a country or region. Smaller ISPs are either connected directly to these backbones or to a larger regional ISP that is connected to one. The backbones themselves are interconnected at various access points called "NAPs." Major backbone providers worldwide include Level 3 Communications, NTT, GTT, Tata Communications, Telia Carrier, CenturyLink, AT&T, Verizon and Sprint. See NAP.