The Internet today is not a simple hierarchical structure. It is made up of many wide
and local area networks joined by connecting devices and switching stations. It is
difficult to give an accurate representation of the Internet because it is continuously
changing—new networks are being added, existing networks need more addresses, and
networks of defunct companies need to be removed. Today most end users who want
Internet connection use the services of Internet service providers (ISPs). There are
international service providers, national service providers, regional service providers,
and local service providers. The Internet today is run by private companies, not the
government. Figure 1.1 shows a conceptual (not geographical) view of the Internet