The ISPs short term for Internet Service Providers is the gateway to your wonder World of Internet. They give different types of access to Internet. The types of connection are broadly defined as per the equipment and its type of connection used to connect you to the Internet.
The Analog connection called as a Dial- up access was the earliest ways by which connections were established to the Internet using the Telephone Lines. It is both economical and slow. You use a Modem connected to your PC, and dial a phone number to connect to the Network. Typical Dial-up connection speeds range from 2400 bps to 56 Kbps.
The next better option came in the way of ISDN connections or Integrated Services Digital Network (ISDN) for sending Voice, Video, and Data over digital Telephone lines or normal Telephone wires. Speeds range from 64 Kbps to 128 Kbps. The B-ISDN, the Broadband ISDN is similar to ISDN but it transfers data over Fiber Optic Telephone lines.
The DSL has become the standard way to connect to the Internet and it provides an always on connection because it uses existing 2-wire copper telephone line and is always on. The two main categories of DSL for home subscribers are called ADSL and SDSL.
The ADSL short for Asymmetric Digital Subscriber Line supports Data rates of from 1.5 to 9 Mbps when receiving data (known as the downstream rate) and from 16 to 640 Kbps when sending data (known as the upstream rate). ADSL requires a special ADSL modem.
The SDSL, short for symmetric digital subscriber line, a Technology that allows more data to be sent over existing Copper Telephone Lines and supports data rates up to 3 Mbps. SDSL works by sending digital pulses in the high-frequency area of Telephone wires and can not operate simultaneously with voice connections over the same wires.
The VDSL or Very High DSL (VDSL) is a DSL technology that offers fast data rates over relatively short distances — the shorter the distance, the faster the connection rate.
Internet is provided in modern times through Cable TV lines by use of a Cable Modem and you get a broadband Internet and the Cable speeds range from 512 Kbps to 20 Mbps.
Wireless Internet Connection is one of the newest Internet connection types by using Radio frequency bands providing an always-on connection which can be accessed from anywhere.
In addition to these types of basic connections we have more types of leased lines like T1, T2, and T3 connections which are fully dedicated Lines giving exclusive access to Internet at much faster Data transfer speeds.