International service providers are used to connect nations together.
National service providers are backbone networks created and maintained by specialized companies. There are many such service providers operating in North America. Some of the very well known are sprint link, AGIS, and internet MCI. To provide connectivity between end users, these backbone networks are connected by complex switching stations (usually run by third party) called network access points or NAPs
Regional internet service providers are smaller ISPs that are connected to one or more national service providers. They have lesser data rate.
Local internet service providers are used to provide direct service to the end users. The local ISPs can be connected to regional ISPs or directly to national service providers. Most of the end users are connected to the local ISPs.