@VisibleForTesting
    static boolean validateClientAcknowledgement(final long h, final long oldH, final Long lastUnackedX) {
        if (lastUnackedX == null) {
            // No unacked stanzas.
            return h == oldH;
        }

        return h <= 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