A replaceable nasal interface system including a molded air tube having a generally D-shaped cross section, and including first and second lumens. The disc-facing surface comprises an inside set of surface components that includes an inside cavity dam and an inside sub-ambient pressure cavity having an inside cavity floor. As the packet is being received, segmentation cells are created from portions of the packet received where each segmentation cell is provided to a switching fabric as soon as creation of the segmentation cell is completed.