B. Design specifications to consider for the MDF: 1  The MDF is generally located in the basement or bottom floor of a building. IDF's located on the floors above are generally stacked above the MDF to allow for ease of cable distribution and limit cable distances. Cable distance is an important factor for data users. Most data communications systems are limited to 300' maximum, to allow for 100Mbps over 24 AWG twisted pair telephone cable.