A duration to transmit multiple messages is calculated. A first request based on the calculated duration is transmitted. The first request is a request for reserving a time period to transmit. In response to receiving an approval of the first request, for each message in the multiple messages, a transmit time is calculated. A determination is made that a current time exceeds a particular transmit time for a particular message. In response to the determination, a second request is transmitted. The second request is a request for permission to transmit. In response to receiving an approval of the second request, the particular message is transmitted.