Internet service provider (ISP)

Definition of Internet service provider (ISP) in The Network Encyclopedia.

What is ISP (Internet Service Provider)?

A company that provides individual users and businesses with connectivity to the Internet. Internet service providers (ISPs) also provide clients with access to Internet services such as Web hosting, Simple Mail Transfer Protocol (SMTP) mail, Usenet newsgroups, Internet Relay Chat (IRC), and downloadable Internet software.

ISPs come in various shapes and sizes, from volunteer-run freenets to local, regional, and national service providers such as America Online. Many smaller ISPs, especially those that originated in a university environment, still use freely available software such as Linux, Apache’s Web server, and Sendmail for providing services to customers.

Larger ISPs often use a heterogeneous network in which Internet Information Services (IIS) and Microsoft Exchange Server play an essential role by providing core Web and mail services, as well as support for advanced Web and e-commerce applications for business and corporate clients.