An Internet service provider (ISP) is a company that provides customers with Internet access. 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, may be provided as well. The services and service combinations may be unique to each ISP.
An Internet service provider is also known as an Internet access provider (IAP).
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.
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.
A uniform resource locator (URL) is the address of a resource on the Internet. A URL indicates the location of a resource as well as the protocol used to access it.
A URL contains the following information:
- The protocol used to a access the resource
- The the location of the server (whether by IP address or domain name)
- The port number on the server (optional)
- The location of the resource in the directory structure of the server
- A fragment identifier (optional)
Also known as a Universal Resource Locator (URL) or Web address. A URL is a type of uniform resource identifier (URI). In common practice, the term URI isn’t used, or is used synonymously with URL, even though this is technically incorrect.
Tim Berners-Lee and the Internet Engineering Task Force working group is credited with developing the URL in 1994. It is formally specified in RFC 1738.
All URLs are presented in the following order:
- Scheme name
- Colon and two slashes
- Location of the server
- The port (optional) and the location of the resource on the server
- Fragment identifier (optional)