Abstract: An access node for digital subscriber line (DSL) communication comprising a transceiver configured to couple to a subscriber line, and a control entity coupled to the transceiver, wherein the control entity is configured to receive a request to switch to a nominal asymmetry ratio between an upstream data rate and a downstream data rate after initialization of the subscriber line, determine a flexible time period value based on the nominal asymmetry ratio, wherein the flexible time period is used to define a time division duplexing (TDD) frame structure, and forward a message that comprises the flexible time period value to the transceiver, wherein the transceiver is configured to transmit an upstream transmission using the TDD frame structure over the subscriber line, and receive a downstream transmission using the TDD frame structure over the subscriber line.