1. A method of configuring a data network, the method comprising: determining a bandwidth capacity of a communications link connecting a digital subscriber line access multiplexer (DSLAM) and an asynchronous transfer mode (ATM) switch based on a first user type selected from a plurality of user types, each of the plurality of user types having a different bandwidth capacity; determining an average peak bandwidth per user value based on the first user type; determining a data transmission slowdown indicator that includes a slowdown amount and a probability of experiencing a slowdown event; determining an estimated maximum number of users of the first user type for digital subscriber lines that may be supported by the DSLAM, where the estimated maximum number of users of digital subscriber lines is based on the average peak bandwidth per user value, the bandwidth capacity of the communication link, and the customer data transmission slowdown indicator; and configuring the data network such that the DSLAM has a configured number of users of digital subscriber lines that is less than or equal to the estimated maximum number of users of digital subscriber lines.