I have NEVER trusted the on screen network display for accuracy. Pick up "Ethereal", a packet sniffer, and do you own external investigations.
In answer to your question, those are the only two elements that get sent automatically: entity updates and hearthbeats. Functionally they are the same, being sent at the same time, but as JCL states, you can shut everything down except the heartbeat for lacking that is a signal to the server and client that they have been disconnected.
However you are right: at entrate 32, it should theoretically be sending an update every two seconds and then not of 500. Like I said, try an external measure.