h the Internet was designed to function when any route crashes, if the central databases that hold IP addresses are disabled, the Internet won't function. See the section "The Criticality of Root Servers" below for information on root servers. Largest Carriers Worldwide-Backbone Providers The telephone companies with the largest Internet backbones in the United States are Sprint, Verizon, CenturyLink (through its purchase of Level3), and AT&T. There are a number of local carriers (ISPs) that connect users to the Internet because no single provider has service everywhere. According to the May 24, 2017, article by Antoine Gara in the Forbes online article, "The World's Largest www.TechnicalPDF.com Telecom Companies: AT&T & Verizon Top China Telecom," the following are the largest telephone companies by total revenue worldwide. The list includes their headquarters locations. However, most of them have services in other countries as well: AT&T-U.S. Verizon-U.S. China Mobile-Hong Kong, China Nippon Telegraph & Telecom-Japan Softbank-Japan Deutshe Telekom-Germany Telefonica-Spain KDDI-Japan China Telecom-China Using Search Engines to Unleash Vast Stores of Information The introduction of sophisticated search engines by organizations such as Google, Microsoft, and Yahoo! (part of Verizon) made browsing the Internet convenient by organizing the enormous amounts of information available on the Internet. Search engines from Google and Baidu in China and others including DuckDuck Go Search, Bing (part of Microsoft), Dogpile Search, Yippy Search, and Webopedia Search earn revenue from advertising on their sites and from ranking companies that pay fees for higher placements (rankings) in search results. Page ranking refers to the placement on a web page of search results. Ranking a product or service higher places it closer to the top of search results, with a higher likelihood of people clicking on the link. In addition to paying for higher ranks, ranking is done by analyzing the number of other sites that link to a particul