DSL Service Starts With the Phone Company

• Most providers of Digital Subscriber Line (DSL) service are local telephone companies. These companies allow the DSL service to ride their existing copper wires between the residence or business and the local central office where commercial-grade telecom equipment resides. From the central office, DSL traffic passes through a series of multiplexers, aggregators and high speed data switches until it reaches either its destination or the Internet backbone.
  
  

The DSL Connection to a Home or Office Is Called a "Pipe"

• DSL service consists of two high-level components: the copper wire that physically connects the home or office to the telephone company central office, and the logical provisioning that is done on telephone company equipment to enable DSL service. Because these components combine to create a data connection through which subscribers can push files, pictures, music, and other data, the connection is often referred to as a "pipe."
  
  

The "Size" of the Pipe Is the Bandwidth

• When the telephone company provides new DSL service, it allocates a certain amount of bandwidth to the customer's line. This bandwidth--the amount of simultaneous data that can be pushed through the DSL pipe in a given amount of time--is generally referred to as the "size" of the DSL pipe. A "bigger pipe" indicates higher bandwidth, or the ability to push more data through the DSL connection at the same time. A smaller pipe is the opposite--a lower bandwidth that doesn't allow as much data to pass through, leading to slower transfer times.
  
  

The Users Modem Connects to the Internet

• Once the service has been provisioned, the telephone line installed, and the modem delivered, a customer is ready to connect to the Internet. When the user turns on her modem, the modem connects across wires to the local DSL access multiplexer where it registers its user credentials and establishes a connection. The multiplexer is, in turn, connected to an aggregator in the area which is subsequently connected to a larger commercial-grade switch (such as an ATM or Ethernet switch). This series of connections allows the end user to exchange data through her own pipe with any connected computer or network in the world.