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ISPs provide connections into the Internet for home users and businesses. There are local, regional, national, and global ISPs. However, the regional and national providers that provide bandwidth, transit, and routing services are more appropriately called NSPs (network service providers). The interconnection scheme is hierarchical in most cases, with local ISPs connecting into regional NSPs that, in turn, connect into national or global NSPs. These connections are discussed under "Internet Architecture and Backbone."

An ISP is usually a local service provider that is in the business of providing customers with Internet access and customer support. In contrast, the NSPs are more interested in network infrastructure and reselling bandwidth. Many ISPs are small offices with very little equipment. The ISP outsources all its equipment needs with an NSP or collocates equipment at a carrier or NSP POP (point of presence).