Service providers deploy DSL connections in the last step of a local telephone network, called the local loop or last mile. The connection is set up between a pair of modems on either end of a copper wire that extends between the customer premises equipment (CPE) and the DSL access multiplexer (DSLAM). A DSLAM is the device located at the Central Office (CO) of the provider and concentrates connections from multiple DSL subscribers. A DSLAM is often built into an aggregation router.
Figure 1 shows the equipment needed to provide a DSL connection to a SOHO. The two components are the DSL transceiver and the DSLAM:
- Transceiver - Connects the computer of the teleworker to the DSL. Usually the transceiver is a DSL modem connected to the computer using a USB or Ethernet cable. Newer DSL transceivers can be built into small routers with multiple 10/100 switch ports suitable for home office use.
- DSLAM - Located at the CO of the carrier, the DSLAM combines individual DSL connections from users into one high-capacity link to an ISP, and therefore, to the Internet.
Figure 2 depicts modern DSL routers and broadband aggregation routers. The advantage that DSL has over cable technology is that DSL is not a shared medium. Each user has a separate direct connection to the DSLAM. Adding users does not impede performance, unless the DSLAM Internet connection to the ISP, or the Internet, becomes saturated.