A system and method for allowing flexible associations between PHY devices and MAC devices in a point-to-multipoint communications system, such that a given upstream channel is not deterministically bound to a particular MAC device. An upstream MAC device may connect to a varying number of PHY devices depending on configured PHY capacity. Upstream service flows are intact by noting Service identifiers (SIDs) of each burst received at a PHY device. A burst is then directed via a switching infrastructure to the appropriate MAC on the basis of the SID.