A data rate control system for an optical line terminal (OLT) may include a processor, an OLT Medium Access Control (MAC) device that includes passive optical network (PON) ports that are mapped to identifiers, and a switch device coupled to the OLT MAC device. The OLT MAC device may determine that a PON port is congested, and may transmit a message to the switch device indicates the congestion at the PON port based on the mapped identifier. The switch device may transmit data items to the OLT MAC device for transmission over the PON ports at data rates respective to the PON ports, may receive the message, and may reduce the rate at which the data items are being transmitted to the OLT MAC device for transmission over the congested PON port without changing the rates at which other data items are being transmitted to the OLT MAC device.