Internet Backbone

The Internet backbone refers to the principal data routes between large, strategically interconnected networks and core routers on the Internet. These data routes are hosted by commercial, government, academic and other high-capacity network centers, the Internet exchange points and network access points, that interchange Internet traffic between the countries, continents and across the oceans of the world. Internet service providers (often Tier 1 networks) participate in Internet backbone exchange traffic by privately negotiated interconnection agreements, primarily governed by the principle of settlement-free peering.

Read more about Internet Backbone:  History, Architectural Principles, Infrastructure, Modern Backbone