Backbone in telecommunications refers to the network infrastructure that makes up a network.  It can apply to a business, or the entire Internet. They are considered the largest networks in the world and the building blocks for Wide Area Networks (WANs). Backbones are used mostly by large commercial organizations, as well as educational and government institutions where efficiency and security are of the utmost importance. 

Backbone service providers either own, rent, or share the physical lines that make up the backbone. An ISP (Internet Service Provider) can own their own backbone, or lease it from a carrier provider.  The ISP can then create its own backbones for institutional customers while they maintain the physical lines for each network created. The customer owns the unique sites and offices on the real estate side that makes the network. Backbone Illinois networks are maintained by the ISP, they are responsible for guaranteeing stability and redundancy. This comes at a high price for the institution that requires such a large network, especially for International businesses with networks that require lines running through entire oceans.