Establishing a Physical Path from the Customer to the Telco

One end of the cable is inside a CO, which is where the telco keeps the equipment used to create the telephone network. Generically speaking, the switches in the CO are called telco switches, phone switches, or WAN switches. There are lots of other names for specific types of equipment that the telco uses in the CO. The cable is plugged into a physical interface in a telco switch in the CO, with the other end of the cable connecting to the router at the customer site.

The cable runs from the CO, typically underground, and then comes up into the customer building. Installing the cable requires the right-of-way to go under the street, block traffic, and dig up a street or yard to run the cable. Thinking ahead, the telco often runs extra wires between the CO and large buildings, office complexes, and other business centers, just so it doesn't have to interrupt traffic and dig up the earth all the time.

To complete the path between Atlanta and Cincinnati, you'll need two more things. First, you need a similar cable run from the office building in Cincinnati where the other router sits and the telco CO in Cincinnati. The other requirement is that the telco needs to somehow get the electrical signals between the Atlanta CO and the Cincinnati CO. To do so, the telco does something like what is shown in Figure 14-3.