RACK_sent_after(t1, seq1, t2, seq2):
    If t1 > t2:
        Return true
    Else if t1 == t2 AND seq1 > seq2:
        Return true
    Else:
        Return false

RACK_update():
    For each Segment newly acknowledged, cumulatively or selectively,
    in ascending order of Segment.xmit_ts:
        rtt = Now() - Segment.xmit_ts
        If Segment.retransmitted is TRUE:
            If ACK.ts_option.echo_reply < Segment.xmit_ts:
               Continue
            If rtt < RACK.min_rtt:
               Continue

        RACK.rtt = rtt
        If RACK_sent_after(Segment.xmit_ts, Segment.end_seq
                           RACK.xmit_ts, RACK.end_seq):
            RACK.xmit_ts = Segment.xmit_ts
            RACK.end_seq = Segment.end_seq