A Combinatorial Analysis of the Main Distributing Frame: Spare Requirements for Conversion to Preferential Assignment from Random Assignment

The Main Distributing Frame (MDF) is that equipment in a central office building whose main function is to permit the flexible interconnection of cable from outside the building to central office equipment inside the building. This primary function accounts for most of the terminal capacity of a typical M D F . The remaining capacity serves a wide variety of other cross-connecting functions ranging from tying together two outside plant cable pairs to cross-connecting two or more pieces of central office equipment. The conventional M D F is a double-sided steel structure with protectors or terminal strips mounted on one side, and terminal strips on the other. These are referred to as the "verticals" and "horizontals" due to their mounting orientation. The vertical side is the part of the M D F where the outside cable is terminated. The horizontal side is the part of the M D F where cables, which connect to the equipment of a central office (mainly line and trunk equipment), are usually terminated. To provide the maximum capacity of interconnections as well as complete flexibility in the connection of any outside plant equipment to any central office equipment, administration of the M D F must result in small numbers of long cross-connections. This can only 2465