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An Internet service provider (ISP) is a company that provides customers with Internet access. It is often referred to as just “the provider.” Data may be transmitted using several technologies, including dial-up, DSL, cable modem, wireless or dedicated high-speed interconnects.
Typically, ISPs also provide their customers with the ability to communicate with one another by providing Internet email accounts, usually with numerous email addresses at the customer’s discretion.
Other services, such as telephone and television services, or personal websites or home pages may be provided as well. The services and service combinations may be unique to each ISP.
Today, ISPs are usually cable companies or mobile phone companies that offer Internet subscriptions in addition to TV or mobile communications services.
An Internet service provider is also known as an Internet access provider (IAP).
In a nutshell, to be able to connect a device such as a personal computer (PC) to the internet, special networking, telecommunications, and routing equipment is required. Since the vast majority of consumers do not have access to this kind of equipment, ISPs “rent” them access to networks that enables users to establish Internet connectivity, maintain infrastructures, and resolve domain names.
Some ISPs offer Internet access for free, usually for a limited amount of hours per day at a limited speed. These so-called “freenets” usually generate revenue by including banners or other ads.
The Internet began as a closed network between government research laboratories and universities and colleges. As universities and colleges began giving Internet access to their faculty and other employees, ISPs were created to provide Internet access to those employees at home and elsewhere. The first ISP began in 1990 as The World, based in Brookline, Massachusetts.
Individual customers and businesses pay ISPs for Internet Access. ISPs are interconnected to one another at network access points. In turn, ISPs pay other, larger ISPs for their internet access, which in turn pay still other ISPs.
This cascades multiple times until transmissions reach a Tier 1 carrier, which is an ISP capable of reaching every other network on the internet without purchasing IP transit or paying settlements. However, it is difficult to determine the status of a network because the business agreements to pay settlements are not made public. Also, traffic is always routed through several networks, jumping back and forth from Tier 1 carriers to Tier 2 and 3 several times before data reaches its destination.
However, the situation is more complex than simply a single connection established to an upstream ISP. ISPs may have more than one point of presence (PoP), which is an access point to the Internet comprised of a physical location housing servers, routers, ATM switches and digital/analog call aggregators.
Some ISPs have thousands of PoPs. Multiple PoPs may have separate connections to an upstream ISP. And each ISP may have upstream ISPs and connections to each one of them at one or multiple PoPs.