TLP_send_probe():

    If TLP.end_seq is None and
       Sender has taken a new RTT sample since last probe or
       the start of connection:
        TLP.is_retrans = false
        Segment = send buffer segment starting at SND.NXT
        If Segment exists and fits the peer receive window limit:
           /* Transmit the lowest-sequence unsent Segment */
           Transmit Segment
           RACK_transmit_data(Segment)
           TLP.end_seq = SND.NXT
           Increase FlightSize by Segment length
        Else:
           /* Retransmit the highest-sequence Segment sent */
           Segment = send buffer segment ending at SND.NXT
           Transmit Segment
           RACK_retransmit_data(Segment)
           TLP.end_seq = SND.NXT
           TLP.is_retrans = true

    If FlightSize is not zero:
        Rearm RTO timer to fire at timeout = now + RTO