Internet Access Guide : Dial-Up

Picture: Dial-Up Internet access
A voice modem dials an ISP number that connects it to one of the ISP's modems.
The connection goes through the telephone network.

Dial-up Internet access has been offered since the beginning of the Internet. In dial-up access, a voiceband modem at a subscriber site communicates with the corresponding modem at her ISP site over the telephone network (PSTN) during an Internet connection. The ISP gives her a phone number that must be dialed to initiate communication with one of the ISP's modems. The PSTN treats dial-up Internet signal in the same way as voice signal. Because PSTN is a circuit switched network, a dial-up Internet subscriber occupies a dedicated circuit during the Internet connection.

The maximum data rate that can be achieved with dial-up Internet access depends on the type of modems employed at the subscriber site and at the ISP. Nowadays, most modems support either V.90 or V.92 modem standard. Both standards give downstream data rate up to 56 kbps. Upstream data rate of V.90 is 33 kbps, while V.92 can reach 33 - 48 kbps. V.92 also supports Modem On Hold feature, that's you can suspend your Internet session to receive a telephone call and get back to the Internet when the call ends. Real world performance of dial-up Internet access depends also on the connection from the ISP to backbone network and Internet traffic load.