The technology is directed to the use of a bitmap generated at a receiver to track the status of received packets sent by a transmitter. The technology may include a network device including an input port, output port, and circuitry. The circuitry may generate a transmitter bitmap that tracks each data packet sent to another network device. The circuitry of the network device may receive, from the other network device, a receiver bitmap that identifies each data packet that is received and not received from the network device. The circuitry may then determine which data packets to retransmit by comparing the transmitter bitmap to the receiver bitmap.