private synchronized boolean validateClientAcknowledgement(long h) {
        if (h < 0) {
            throw new IllegalArgumentException("Argument 'h' cannot be negative, but was: " + h);
        }
        if (h > MASK) {
            throw new IllegalArgumentException("Argument 'h' cannot be larger than 2^32 -1, but was: " + h);
        }
        final long oldH = clientProcessedStanzas.get();
        final Long lastUnackedX = unacknowledgedServerStanzas.isEmpty() ? null : unacknowledgedServerStanzas.getLast().x;
        return validateClientAcknowledgement(h, oldH, lastUnackedX);
    }
Checks if the amount of stanzas that the client acknowledges is equal to or less than the amount of stanzas that
we've sent to the client.

@param h Then number of stanzas that the client acknowledges it has received from us.
@return false if we sent fewer stanzas to the client than the number it is acknowledging.
xmppserver/src/main/java/org/jivesoftware/openfire/streammanagement/StreamManager.java