You will notice that when T-1 lines are installed one has to make a number of choices. One has to choose the carrier, the location of the demarcation point and the type of channel service unit also called the CSU. You may also have to choose the data service unit or the DSU to be used. Another selection has to be made in the WAN IP router that has to be used and the type of speeds. There are specialized WAN routers that are used with T-1 lines to route Internet or VPN data onto the T-1 line. This is carried from the subscriber TCP/IP network by using the customer premises equipment or the CPE. Most of the T-1 providers maintain and sell the CPE as part of the service contract.