For bandwidth utilization, I have used MRTS-MRTG on several sites and I have been happy.
If you are a Unix user, you may follow the following howto (though it was meant for FreeBSD, you can easily figure your way out, I am sure):
http://www.bjou.de/blog/mrts-mrtg-rrdtool-total-statistics/For network utilization, I am sorry I either don't understand what you are referring to or it's because I concentrate more on systems than network side of things.