A single switch fabric-based, multi-channel bank digital subscriber line
access multiplexer includes a master channel bank containing a master
switch module in which the switch fabric and a downstream-directed
traffic scheduler reside, and one or more expansion channel banks that
are linked with the master channel bank by way of upstream and downstream
communication links. Distributed among the channel banks are respective
policing mechanisms and cell rate control mechanisms that control
upstream-directed communications from line card ports of each expansion
channel bank to the switch fabric. Downstream data transmissions are
locked to network timing, and are scheduled by a centralized scheduling
mechanism resident in the master channel bank.