Voice Over IP

ISPs AND THE TELEPHONE NETWORK

The Internet Service Providers (ISPs) provide the access into the Internet. They provide this access through the telephone network, and the Internet user (say from the home) uses a dial-up modem to connect to the ISP through the telco local exchange carrier (LEC), and the LEC central office (CO), see Figure 2-2.

The telephone companies are required to provide the ISPs with connections to the telephone company's customers. The connections are provided at the telco's plant. These connections from the customer to the CO's main distribution frame (MDF, a physical "patch panel") may be patched to the local switch (a conventional circuit switch, for example). Alternately, the line from the customer may be patched to a ...