Dialup

Dial-up refers to Internet access delivered over the public switched telephone network (PSTN) using a dial-up modem and a standard telephone line. A user’s computer dials a modem at an Internet service provider (ISP); after a handshake, the ISP assigns an IP address and the connection is established through a protocol such as PPP (Point-to-Point Protocol) or SLIP. Data is transmitted as audio over the analog line, which imposes speed and quality limitations.

Speeds associated with dial-up are typically up to 56 kilobits per second (kbps) under ideal conditions, with real-world performance often lower due to line quality, line noise, and protocol overhead. Early modem generations operated at much lower speeds, measured in baud rather than bits per second. In many regions, dial-up connections were billed per minute and required the line to be occupied for the duration of the session.

Technical and logistical considerations include the fact that dial-up uses the same telephone line as voice service, so the line must be free for data transmission; this prevents simultaneous voice calls unless a second line is available. Modems can be internal or external, and ISPs typically provided a dedicated dial-in number or a set of numbers to handle multiple users.

Historical context and decline: Dial-up gained widespread use in the 1990s and early 2000s as the primary form of consumer Internet access. It has largely been supplanted by broadband technologies such as DSL, cable, and fiber, which offer always-on connections with higher speeds and lower latency. Nevertheless, dial-up remains available in some rural or remote areas, or as a backup option for legacy systems and devices.

Security considerations: dial-up connections are generally unencrypted by default, though PPP can include authentication. Without additional protections, signals can be vulnerable to eavesdropping or unauthorized access on unsecured lines.