You could use a great tool called <a href=”http://www.wireshark.org/download.html”>Wireshark</a>, it used to be called ethereal, to do this task.
Wireshark is free! (You pay for support) and will tell you much of the information you are looking for. Do keep in mind though that you’ll need to either configure a shiffer port on your core switch (or switches) if you have switches, since the traffic isn’t sent to all ports on a switch by default. If you only have hubs this isn’t a concern.
Also, if you have switches (and you’re wanting trending– not analysis) you could use another FREE piece of software called <a href=”http://oss.oetiker.ch/mrtg/download.en.html”>MRTG </a>to show you traffic patterns on your switches down to the port level and/or another piece of software called <a href=”http://www.snapfiles.com/get/prtg.html”>PRTG </a>to show you the traffic trends on your servers.