aeron-driver/src/main/java/io/aeron/driver/PublicationImage.java
int initiateAnyRttMeasurements(final long nowNs)
    {
        int workCount = 0;

        if (congestionControl.shouldMeasureRtt(nowNs))
        {
            final long preciseTimeNs = nanoClock.nanoTime();

            channelEndpoint.sendRttMeasurement(imageConnections, sessionId, streamId, preciseTimeNs, 0, true);
            congestionControl.onRttMeasurementSent(preciseTimeNs);

            workCount = 1;
        }

        return workCount;
    }
int initiateAnyRttMeasurements(final long nowNs)
    {
        int workCount = 0;

        if (congestionControl.shouldMeasureRtt(nowNs))
        {
            final long preciseTimeNs = nanoClock.nanoTime();

            channelEndpoint.sendRttMeasurement(imageConnections, sessionId, streamId, preciseTimeNs, 0, true);
            congestionControl.onRttMeasurementSent(preciseTimeNs);

            workCount = 1;
        }

        return workCount;
    }
Called from the {@link Receiver} thread to check for initiating an RTT measurement.

@param nowNs in nanoseconds
@return number of work items processed.