A multiplexing card comprises a primary TDM port over which TDM frames are communicated to and from a networking device, a plurality of secondary TDM ports over each of which fractional TDM frames are communicated to and from a plurality of digital subscriber line (DSL) units; and a logic device coupled between the primary TDM port and the plurality of secondary TDM ports, wherein the logic device is operable to map timeslots from each of the fractional TDM frames received over the plurality of secondary TDM ports to timeslots in a TDM frame communicated over the primary TDM port, and to map each of a plurality of blocks of timeslots in a TDM frame received over the primary TDM port to one of the plurality of secondary TDM ports; wherein the combined number of timeslots containing user data in the fractional TDM frames received over the plurality of secondary TDM ports is less than or equal to the maximum number of available timeslots in the corresponding TDM frame communicated over the primary TDM port.