Internet Access Services and Protocols

Residential Internet Access

If you want the Internet at home or in an office, there are several ways to connect. Dial-up using a modem still exists in some areas, but ADSL, cable modems, and wireless options like Wi-Fi are much more common. These connections rely on different physical media—twisted pair cables, coaxial lines, optical fiber, satellites, or radio waves. Each medium has its strengths, but the goal is simple: get a stable, reliable connection that keeps your devices online.

Common Protocols for Serial Connections

Two protocols have been historically important for sending Internet data over serial connections: SLIP (Serial Line Internet Protocol) and PPP (Point-to-Point Protocol).

SLIP

Fig : SLIP

SLIP is very simple. It was originally designed to connect Sun workstations over dial-up modems. It marks the end of a data packet with a special character, decimal 192. But SLIP has major limitations: it does not perform error detection or correction, cannot assign dynamic IP addresses, requires pre-assigned IP addresses, and offers no authentication. Because of this, it’s no longer widely used.

PPP

PPP replaced SLIP and solved most of these problems. It’s the protocol your ISP likely uses to connect your home PC to the Internet. PPP provides error detection, authentication, and link management. It’s flexible enough to support modern residential connections over ADSL, cable, or wireless links.

 

Fig : PPP

How PPP Works

 

Fig : PPP Architecture

PPP defines several control protocols that handle different tasks. The Link Control Protocol (LCP) establishes, maintains, configures, and terminates the connection between your computer and the ISP. The Authentication Protocol verifies your identity, making sure only authorized users can access the network. The Network Control Protocol (NCP) takes over once the link is established and the user is authenticated. NCP configures the network layer and allows your computer to exchange data with the ISP. Each network protocol, like IPv4 or IPv6, has its own NCP that manages data encapsulation and delivery.

In short, PPP ensures that your connection is reliable, authenticated, and ready to carry Internet traffic from your home to your ISP and out to the world.