> The transmitting host SHOULD send the first zero-window > probe when a zero window has existed for the retransmission > timeout period (see Section 4.2.2.15), and SHOULD increase > exponentially the interval between successive probes.
that first part requires an action in a given case, to ensure it is done (the context is given by some preceding text not quoted here). it doesn't specify all cases in which it might be done. having said that, i now suspect that sending one byte into a zero-window is not the problem.
