a transmit re-try buffer for storing packet data received from a first host system serviced by the variable-length packet transmitter;

a write pointer for the transmit re-try buffer, the write pointer indicting a writing location within the transmit re-try buffer to write new packet data received from the first host system, the writing location being advanced as additional packet data is received from the first host system;

a read pointer for the transmit re-try buffer, the read pointer indicting a reading location within the transmit re-try buffer to read packet data from for transmission to a remote receiver;

a serial link to the remote receiver for sending packet data read from the transmit re-try buffer to the remote receiver;

a de-allocation pointer for the transmit re-try buffer, the de-allocation pointer indicting an over-writing location within the transmit re-try buffer wherein the write pointer is prevented from advancing past the de-allocation pointer; and

a reverse channel from the remote receiver for receiving pointer updates from the remote receiver, the pointer updates causing the de-allocation pointer to advance to provide additional space within the transmit re-try buffer for writing packet data from the first host system,

whereby pointer updates from the remote receiver update the de-allocation pointer and the over-writing location in the transmit re-try buffer.